[flang-commits] [flang] [flang] Fix seg fault `CodeGenAction::executeAction()` (PR #78269)

[Kareem Ergawy via flang-commits]

ergawy wrote:

> Thanks!
> 
> It would be good to add a diagnostic and a test - perhaps trying compiling a "broken" MLIR file?

Thanks for the reply @banach-space. I can try to add a unit test (I see there is none for the flang `CodeGenAction` class so far. I think this will be better self-contained and easier to understand what is going on than a lit test. WDYT?

https://github.com/llvm/llvm-project/pull/78269