[clang] [analyzer] Avoid a crash in a debug printout function (PR #79446)

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NagyDonat wrote:

When I added `RangeConstraintManager::printValue()` calls at the top of `evalBinOpNN` (while doing printf-style debugging), I got crashes from the test files `infeasible-sink.c` and `constant-folding-crash.cpp`. I'd guess that getting an empty range set stops the analysis quickly (perhaps via a PosteriorlyOverconstrained state?), but apparently my debug printout was in a location that crashed before this could happen.

https://github.com/llvm/llvm-project/pull/79446