After a failed installation (Composer troubles again) there is an orphaned environment.

The deletion logic needs to go and see if that folder is actually there, not just stop if it cant find the entry in the environments.json.

$ virtphp destroy foo
The environment you specified has not been created.
$ virtphp create foo
Checking current environment
ERROR: The directory for this environment already exists (/Users/phil/.virtphp/envs/foo).

I'll try and get on top of this one soon, but for now it's here.