ACOPF does not handle well non-dispatchable generation results

[Carlos-Alegre]

Describe the bug
After running an adopt with non dispatchable generators, the solver crashes when trying to flush the results
To Reproduce
Steps to reproduce the behavior:

1. Set some generation to enabled_dispatch = False
2. Execute an ACOPF
3. It won't finish since the results object can't handle the non dispatchable generators results.