http://pastebin.com/Zdnkmchy

Description: Ticking block entity

java.lang.NullPointerException: Ticking block entity
at slimeknights.tconstruct.common.Sounds.PlaySoundForPlayer(Sounds.java:46)
at slimeknights.toolleveling.CommonProxy.playLevelupDing(CommonProxy.java:19)
at slimeknights.toolleveling.ModToolLeveling.addXp(ModToolLeveling.java:121)
at slimeknights.toolleveling.ModToolLeveling.afterBlockBreak(ModToolLeveling.java:64)
at slimeknights.tconstruct.library.tools.ToolCore.afterBlockBreak(ToolCore.java:513)
at slimeknights.tconstruct.tools.tools.Hatchet.afterBlockBreak(Hatchet.java:86)
at slimeknights.tconstruct.library.tools.ToolCore.func_179218_a(ToolCore.java:503)
at slimeknights.tconstruct.library.tools.TinkerToolCore.func_179218_a(TinkerToolCore.java:51)
at com.vanhal.progressiveautomation.ref.ToolHelper.damageTool(ToolHelper.java:212)
at com.vanhal.progressiveautomation.entities.chopper.TileChopper.cutTree(TileChopper.java:250)
at com.vanhal.progressiveautomation.entities.chopper.TileChopper.func_73660_a(TileChopper.java:173)
at net.minecraft.world.World.func_72939_s(World.java:1804)
at net.minecraft.world.WorldServer.func_72939_s(WorldServer.java:619)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:709)
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:387)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:613)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:471)
at java.lang.Thread.run(Thread.java:745)

Hm yeah. I guess fake players don't have a connection. Technically a TiC bug

Here is another example
http://pastebin.com/TrGDXGMr

Modpack - Allthemods 1.33

Note: crashes Single player worlds too. Reported for "all the mods" modpack.

Should be fixed in TiC 2.5.6