Issue description:

Crash when entering any other dimension.

What happens:

I set up a small system. I went to the nether and the end. After 10 seconds or so game crashes. And crashes again when relaunched. Unless you can Teleporte out before the 10 seconds. Crash log points to refined storage. I'm sorry I'm on my phone and don't have the log. Will post in a few. I did however find a fix. Chunk loading the area the system is in stopped the crash

What you expected to happen:

Not crash.

Steps to reproduce:

...

Version (make sure you are on the latest version before reporting):

• Minecraft: 1.12
• Forge:
• Refined Storage: latest

Does this issue occur on a server? [yes/no]
haven't tried. Client only at this point

If a (crash)log is relevant for this issue, link it here:

[pastebin/gist/etc link here]
Again will post the rest of the info soon

Please post your crash report

My bad, got busy at work

https://pastebin.com/W3xkScUb

The problem is with an importer connected to a inventory. Said inventory has a "null" item assigned to it, which is not allowed and mods shouldn't handle that. So the implementor of that inventory or chest or whatever the importer is connected to has done it wrong.