Imagery resources and projects succeed when imagery is masked entirely

[tst-nrichman]

Mask options can be utilized in such a way that an imagery resource contains no imagery. When this happens, the imagery resource and project may still succeed in building. However, a database containing a blank imagery project will fail to build.

Steps to reproduce:

1. Install GEE Server
2. Create an imagery resource. For the Mask Type select 'Auto Mask.'
3. Set the Feather value to 255.
4. Set the Tolerance value to 255.
5. Build the resource and preview it. A bounding box should appear with no imagery.
6. Build a project containing the resource.
7. Build a database containing the project. This should fail.