[clang] [analyzer] Fix crash of StreamChecker when eval calling 'fopen' (PR #100990)

[Donát Nagy via cfe-commits]

NagyDonat wrote:

> I decided to put the fixup NFC changes along with this PR (the ones were submitted after I merged the original commit), but on hindsight probably it would be better to merge those NFC changes separately. If you request, I'll split the PR.

Feel free to keep the NFC changes in this commit, just briefly mention them in the description ("This commit also contains some minor NFC code quality improvements." or something similar.) 

https://github.com/llvm/llvm-project/pull/100990