Request type config screen can fail to load in 1.2 if underlying issue types have been removed from the project

Summary

A Service Desk project could have request types where the underlying issues have been removed from the project (issue type scheme), but not deleted.
If a user does NOT have access to any projects where the issue type is actually used, then the request type admin page does not load.

Steps to Reproduce

1. Upgrade an instance with problematic data to Service Desk 1.2.

Expected Results

The upgrade goes ahead without any problems.

Actual Results

The request type configuration screen will fail to load and display a spinning cog.

Workaround

1. Edit the Issue Type Scheme for the project used by the Service Desk and add all available Issue Types.
2. Go back to the requests screen and remove the unwanted request types.
3. Edit the Issue Type Scheme and remove the Issue Types that were just added to workaround the problem.