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

Previously the function `RangeConstraintManager::printValue()` crashed
when it encountered an empty rangeset (because `RangeSet::getBitwidth()`
and `RangeSet::isUnsigned()` assert that the rangeset is not empty).
This commit adds a special case that avoids this behavior.

As `printValue()` is only used by the checker debug.ExprInspection (and
during manual debugging), the impacts of this commit are very limited.

---------

Co-authored-by: Balazs Benics <benicsbalazs@gmail.com>

clang/lib/StaticAnalyzer/Core/RangeConstraintManager.cpp

@@ -3270,6 +3270,10 @@ void RangeConstraintManager::printJson(raw_ostream &Out, ProgramStateRef State,
 void RangeConstraintManager::printValue(raw_ostream &Out, ProgramStateRef State,
                                         SymbolRef Sym) {
   const RangeSet RS = getRange(State, Sym);
+  if (RS.isEmpty()) {
+    Out << "<empty rangeset>";
+    return;
+  }
   Out << RS.getBitWidth() << (RS.isUnsigned() ? "u:" : "s:");
   RS.dump(Out);
 }