Describe the bug

For the Generic System model with Calculate generation profiles and nameplate capacity from open cases on the Power Plant page, when one of the cases being combined generates an SSC simulation error, clicking Select cases causes SAM to crash.

To Reproduce

Steps to reproduce the behavior:

1. Download and open the the "st helena.sam" file attachment to https://sam.nrel.gov/forum/forum-general/4066-combine-cases-shuts-down-sam.html.
2. Go to the "New WT" case and run a simulation to see the SSC error "exec fail(windpower): failed to read local weather file".
3. Go to the "All Wind" case.
4. On the Power Plant page, click Select cases.
5. SAM crashes.

Update: SAM crashes for this file even when there is no SSC simulation error.

Expected behavior

Clicking Select cases should not cause SAM to crash.

If one or more of the cases being combined generates an error, clicking Select Cases should inform the user there is a problem with one of the cases, perhaps in a message box, like "Simulation for case [case name] failed with error: [SSC error]".