I have made RFTools dimensions in FTB Infinity and deleted them after they were no longer needed.
However when clicking on them in the charms GUI, it crashes.

Crash report if needed: http://pastebin.com/uMkqFzfD

This is something that i am aware of and will try to have fixed by the next update.

I've had the same issue with deleting mystcraft worlds.

I could scroll though the saves in the charm (shift+mouse) but could not open the gui and remove them , as it would crash my client as soon as I click on a missing dimension