[clang] [analyzer] Fix a crash from element region construction during `ArrayInitLoopExpr` analysis (PR #113570)

[Donát Nagy via cfe-commits]

https://github.com/NagyDonat approved this pull request.

LGTM, thanks for fixing this crash!

I also happy to see that you simplify the logic and clean up the variable names. (I was a bit curious about the original reason that led to introduce this pattern matching, but I see that you're the original author of this code so I presume that you understand its role.)

https://github.com/llvm/llvm-project/pull/113570