RFtools: rftools-1.10-5.59.jar
MJtyLib: mcjtylib-1.10-2.2.0.jar
Forge: forge-1.10.2-12.18.2.2124-universal.jar

Crash

Need to check if fluidhandler is null:
https://github.com/McJty/RFTools/blob/1.10/src/main/java/mcjty/rftools/blocks/monitor/LiquidMonitorBlockTileEntity.java#L137

Not my bug. Report this to whatever mod the tank above it belongs too. If line 136 in my code returns true then the capability MUST return non null on the line below

@McJty It was your Deep Resonance tank I selected...

What version of Deep Resonance?

Oh then I'll check it out.

deepresonance-1.10-1.2.9.jar

There is a EnderTank(endertanks-1.10.0-1.4.3.jar) in range but it wasn't the one tank selected before the crash.

Edit: And an enderIO fluid conduit.

Ah but that might still cause the problem as it will try to scan them. Can you try to reproduce it without the endertank or with only the endertank?

Seems to only happen when the endertank is there. I've made an issue with the mod author. Would still be good for RFTools to handle the possibility of null. Thanks anyways

I added a safety for this