Fix crash caused by invalid impossible escape keystone

[trimbe]

Fixes #7728

The test variant is generated with conquered keystones, which aren't present in the keystoneMap (and aren't actual mods).

[Mysrt]

If you're like me and bricked your build with this and want to keep working on it go to:

C:\Users<Username>\Documents\Path of Building\Builds<find your build>

• edit the file with notepad/whatever text editor
• ctrl+f for the <Sockets> node
• Delete everything in that node
• save
• should be able to open your build again.
• don't use the jewel again till this is merged in

[Wires77]

We should probably not generate that jewel with conquered keystones, but this is a fine fix for it too.

[trimbe]

I agree, I'll look into making that generation more robust as well.