Leaving world with working builder after rejoin causes following crash:
java.lang.NullPointerException: Ticking block entity
at buildcraft.builders.TileBuilder.instanciateBluePrintBuilder(TileBuilder.java:314)
at buildcraft.builders.TileBuilder$PathIterator.next(TileBuilder.java:149)
at buildcraft.builders.TileBuilder.iterateBpt(TileBuilder.java:360)
at buildcraft.builders.TileBuilder.initialize(TileBuilder.java:222)
at buildcraft.core.TileBuildCraft.func_145845_h(TileBuildCraft.java:81)
at buildcraft.core.builders.TileAbstractBuilder.func_145845_h(TileAbstractBuilder.java:68)
at buildcraft.builders.TileBuilder.func_145845_h(TileBuilder.java:568)
at net.minecraft.world.World.func_72939_s(World.java:1939)
at net.minecraft.world.WorldServer.func_72939_s(WorldServer.java:489)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:636)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:111)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:427)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685)