Deleted instance throws exception

Attempting to start CKAN with multiple instances defined result in an exception if one of the instances is renamed/removed.

The exception thrown is a *NotKSPDirKraken* at CKAN/KSP.cs:58.

I've attached a possible solution, though it might not be the cleanest way to solve this issue.
I'd suggest to also log copious amount of information here, lest things disappear without any apparent reason.