I place and validate a signal block, break a signal, and it crashes.

Crash Report:

---- Minecraft Crash Report ----
// Uh... Did I do that?

Time: 8/18/13 2:19 PM
Description: Ticking tile entity

java.lang.NullPointerException
at mods.railcraft.common.blocks.signals.SignalBlock.isValidPair(SignalBlock.java:78)
at mods.railcraft.api.signals.AbstractPair.getPairAt(AbstractPair.java:109)
at mods.railcraft.common.blocks.signals.SignalBlock.getSignalAt(SignalBlock.java:46)
at mods.railcraft.common.blocks.signals.SignalBlock.determineAspect(SignalBlock.java:122)
at mods.railcraft.common.blocks.signals.SignalBlockRelay.updateSignalAspect(SignalBlockRelay.java:33)
at mods.railcraft.common.blocks.signals.SignalBlock.tickServer(SignalBlock.java:213)
at mods.railcraft.common.blocks.signals.TileBoxBlockRelay.func_70316_g(TileBoxBlockRelay.java:72)
at net.minecraft.world.World.func_72939_s(World.java:2204)
at net.minecraft.world.WorldServer.func_72939_s(WorldServer.java:548)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:666)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:585)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:129)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:482)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:582)

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Stacktrace:
at mods.railcraft.common.blocks.signals.SignalBlock.isValidPair(SignalBlock.java:78)
at mods.railcraft.api.signals.AbstractPair.getPairAt(AbstractPair.java:109)
at mods.railcraft.common.blocks.signals.SignalBlock.getSignalAt(SignalBlock.java:46)
at mods.railcraft.common.blocks.signals.SignalBlock.determineAspect(SignalBlock.java:122)
at mods.railcraft.common.blocks.signals.SignalBlockRelay.updateSignalAspect(SignalBlockRelay.java:33)
at mods.railcraft.common.blocks.signals.SignalBlock.tickServer(SignalBlock.java:213)
at mods.railcraft.common.blocks.signals.TileBoxBlockRelay.func_70316_g(TileBoxBlockRelay.java:72)

-- Tile entity being ticked --
Details:
Name: RCTileStructureSignalBox // mods.railcraft.common.blocks.signals.TileBoxBlockRelay
Block type: ID #456 (tile.railcraft.signal // mods.railcraft.common.blocks.signals.BlockSignal)
Block data value: 12 / 0xC / 0b1100
Block location: World: (22,68,275), Chunk: (at 6,4,3 in 1,17; contains blocks 16,0,272 to 31,255,287), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Actual block type: ID #456 (tile.railcraft.signal // mods.railcraft.common.blocks.signals.BlockSignal)
Actual block data value: 12 / 0xC / 0b1100
Stacktrace:
at net.minecraft.world.World.func_72939_s(World.java:2204)
at net.minecraft.world.WorldServer.func_72939_s(WorldServer.java:548)

-- Affected level --
Details:
Level name: Roller Coaster
All players: 0 total; []
Chunk stats: ServerChunkCache: 625 Drop: 0
Level seed: 1617558688187107600
Level generator: ID 00 - default, ver 1. Features enabled: true
Level generator options:
Level spawn location: World: (180,64,248), Chunk: (at 4,4,8 in 11,15; contains blocks 176,0,240 to 191,255,255), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 9679 game time, 31556 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 129560 (now: false), thunder time: 134342 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:666)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:585)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:129)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:482)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:582)

-- System Details --
Details:
Minecraft Version: 1.6.2
Operating System: Mac OS X (x86_64) version 10.6.8
Java Version: 1.6.0_45, Apple Inc.
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
Memory: 133180752 bytes (127 MB) / 311709696 bytes (297 MB) up to 1069416448 bytes (1019 MB)
JVM Flags: 1 total; -Xmx1G
AABB Pool Size: 2816 (157696 bytes; 0 MB) allocated, 2816 (157696 bytes; 0 MB) used
Suspicious classes: FML and Forge are installed
IntCache: cache: 0, tcache: 0, allocated: 1, tallocated: 63
FML: MCP v8.04 FML v6.2.43.828 Minecraft Forge 9.10.0.828 42 mods loaded, 42 mods active
mcp{8.04} Minecraft Coder Pack Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
FML{6.2.43.828} Forge Mod Loader Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Forge{9.10.0.828} Minecraft Forge Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
CodeChickenCore{0.9.0.3} CodeChicken Core Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Micdoodlecore{} Micdoodle8 Core Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
NotEnoughItems{1.6.1.2} [Not Enough Items](NotEnoughItems 1.6.1.2.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
ImmibisMicroblocks{56.0.3} Immibis's Microblocks Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
AtomicScience{0.7.0} Atomic Science Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
iChunUtil{2.0.0} iChunUtil Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Grinder{2.0.0} Grinder Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BiblioCraft{1.3.4} BiblioCraft Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
ComputerCraft{1.56} ComputerCraft Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
CCTurtle{1.56} ComputerCraft Turtles Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
CountryGamer_PlantsVsZombies{2.3} Plants Vs Zombies Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
ForgeMultipart{1.0.0.106} Forge Multipart Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
ForgeMicroblock{1.0.0.106} Forge Microblocks Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
McMultipart{1.0.0.106} Minecraft Multipart Plugin Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
NBTEdit{1.6.2.0} In-game NBTEdit Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
GalacticraftCore{0.1.39} Galacticraft Core Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
GraviGun{2.0.0} GraviGun Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
ICBM|Contraption{1.3.2} ICBM Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
ICBM|Sentry{1.3.2} ICBM Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
ICBM|Explosion{1.3.2} ICBM Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
LogicalEngineering{0.3.1b} [Logical Engineering](Logical Engineering 0.3.1b.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
mca{3.4.4} [Minecraft Comes Alive](MCA v3.4.4.zip) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
MFFS{3.2.0} Modular Force Field System Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Mekanism{5.5.7} Mekanism Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
MekanismGenerators{5.5.7} MekanismGenerators Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
MekanismTools{5.5.7} MekanismTools Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
powersuits{0.8.0-638} MachineMuse's Modular Powersuits Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Railcraft{8.0.0.0} Railcraft Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
resonantinduction{0.2.0} Resonant Induction Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
StevesCarts{2.0.0.a125} Steve's Carts 2 Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
TrailMix{2.0.0} TrailMix Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
WR-CBE|Core{1.4.0.3} [WR-CBE Core](WR-CBE 1.4.0.3.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
WR-CBE|Addons{1.4.0.3} [WR-CBE Addons](WR-CBE 1.4.0.3.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
WR-CBE|Logic{1.4.0.3} [WR-CBE Logic](WR-CBE 1.4.0.3.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
ImmibisCore{56.0.3} Immibis Core Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
ImmibisMicroblocks_IgnoreThis{56.0.3} Immibis's Microblocks (ignore this duplicate entry, will be fixed eventually) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
IronChest{5.3.20.517} Iron Chest Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
RedLogic{56.0.2} RedLogic Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BasicComponents{1.0.0} Basic Components Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Profiler Position: N/A (disabled)
Vec3 Pool Size: 693 (38808 bytes; 0 MB) allocated, 693 (38808 bytes; 0 MB) used
Player Count: 0 / 8; []
Type: Integrated Server (map_client.txt)
Is Modded: Definitely; Client brand changed to 'fml,forge'