[clang][analyzer] Fix alpha.unix.BlockInCriticalSection for CTU

In CTU there is not always an AnalysisDeclContext for a given call. This
led to crashes. The AnalysisDeclContext access is now checked.

Author: gamesh411

clang/lib/StaticAnalyzer/Checkers/BlockInCriticalSectionChecker.cpp

@@ -14,6 +14,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/Analysis/AnalysisDeclContext.h"
 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
 #include "clang/StaticAnalyzer/Core/Checker.h"
@@ -103,9 +104,10 @@ class RAIIMutexDescriptor {
       // this function is called instead of early returning it. To avoid this, a
       // bool variable (IdentifierInfoInitialized) is used and the function will
       // be run only once.
-      Guard = &Call.getCalleeAnalysisDeclContext()->getASTContext().Idents.get(
-          GuardName);
-      IdentifierInfoInitialized = true;
+      if (AnalysisDeclContext *CalleCtx = Call.getCalleeAnalysisDeclContext()) {
+        Guard = &CalleCtx->getASTContext().Idents.get(GuardName);
+        IdentifierInfoInitialized = true;
+      }
     }
   }