Running a launch config with an invalid tdmlConfig path/name causes the backend to crash

If I change the tdmlConfig.path in a launch config to not point to a valid file, the backend will crash when trying to read the file. There is a stack trace in the terminal output, and a blank error popup appears.

Additionally, if I make the tdmlConfig.name not reflect a test case name in the tdml file, there will be a stack trace and an error popup, but this popup has a somewhat useful message.

Both of these cases should be handled gracefully. Ideally, we shouldn't be throwing an exception that shows up on the terminal output. The error popup is fine, but both cases should have useful, user friendly messages.

Rollback any changes from #1350 or else this will probably be masked.