Provide better error messages when base profiles are setup incorrectly

Due to changing some of my profile names, my Qt profile's base profile no longer existed, and I received:

"ERROR: Module cpp could not be loaded."

Took me a while to figure out why. If a profile's base profile does not exist, we should detect this and display a more accurate error message. And perhaps we could offer a helpful message such as suggesting that the user check their profile / base profile settings.

Saying that a module could not be loaded really seems to indicate an application issue rather than a user issue, so if the message could be changed to detect when this is the user's fault and display a friendlier error, that would help.