[clang] [analyzer] Fix crash when modelling 'getline' function in checkers (PR #145229)

[Baranov Victor via cfe-commits]

================
@@ -1518,14 +1518,19 @@ void MallocChecker::checkGetdelim(ProgramStateRef State, const CallEvent &Call,
   if (!CE)
     return;
 
-  const auto LinePtr =
-      getPointeeVal(Call.getArgSVal(0), State)->getAs<DefinedSVal>();
-  const auto Size =
-      getPointeeVal(Call.getArgSVal(1), State)->getAs<DefinedSVal>();
-  if (!LinePtr || !Size || !LinePtr->getAsRegion())
+  const auto LinePtrOpt = getPointeeVal(Call.getArgSVal(0), State);
+  const auto SizeOpt = getPointeeVal(Call.getArgSVal(1), State);
+  if (!LinePtrOpt || !SizeOpt || LinePtrOpt->isUnknownOrUndef() ||
+      SizeOpt->isUnknownOrUndef())
----------------
vbvictor wrote:

UPD, I forgot about:
```cpp
const CallDescriptionMap<CheckFn> PostFnMap{
      // NOTE: the following CallDescription also matches the C++ standard
      // library function std::getline(); the callback will filter it out.
      {{CDM::CLibrary, {"getline"}, 3}, &MallocChecker::checkGetdelim},
      {{CDM::CLibrary, {"getdelim"}, 4}, &MallocChecker::checkGetdelim},
  };
```
I suppose `CallDescriptionMap` would take care of it. We just need to make sure that we have extract correct types from arguments.

https://github.com/llvm/llvm-project/pull/145229