Issue with coarray lowering

Looks like multiple terminators created
Terminates with
```
error: loc("/app/example.f90":11:3): operation with block successors must terminate its parent block
error: verification of lowering to FIR failed
```
https://godbolt.org/z/fozPsePz7

Start with the Fortran reproducer in the linked Godbolt example and inspect the coarray lowering that produces multiple terminators. Use the reported FIR verification failure as the baseline; done means the reproducer no longer reports a block-termination error and lowering completes successfully.

Written by the indexing model from the issue text.