Remember, this isn't putting fuel into the generator but this happens when trying to go from generator back to inventory via shift clicking.
This happens to me with charcoal. I have yet to try other fuel types. My inventory did have a stack of 20 charcoal and there were 3 left in the generator.
Crash info from java:
Code
java.lang.IndexOutOfBoundsException: Index: 38, Size: 38
at java.util.ArrayList.rangeCheck(ArrayList.java:571)
at java.util.ArrayList.get(ArrayList.java:349)
at dw.a(SourceFile:272)
at ic2.ContainerIC2.transferToSlots(ContainerIC2.java:106)
at ic2.ContainerIC2.a(ContainerIC2.java:59)
at dw.a(SourceFile:110)
at ob.a(PlayerController.java:144)
at id.a(SourceFile:170)
at da.f(SourceFile:120)
at da.e(SourceFile:108)
at net.minecraft.client.Minecraft.k(SourceFile:1299)
at net.minecraft.client.Minecraft.run(SourceFile:754)
at java.lang.Thread.run(Thread.java:679)