Index: clang/lib/Analysis/ThreadSafety.cpp
===================================================================
--- clang/lib/Analysis/ThreadSafety.cpp
+++ clang/lib/Analysis/ThreadSafety.cpp
@@ -1935,6 +1935,10 @@
                       CapDiagKind);
 
   if (isScopedVar) {
+    // The default value for the argument VD to the current function is
+    // nullptr. So we assert that VD is non null because we deref VD here.
+    assert(VD && "!VD");
+
     // Add the managing object as a dummy mutex, mapped to the underlying mutex.
     SourceLocation MLoc = VD->getLocation();
     DeclRefExpr DRE(VD->getASTContext(), VD, false, VD->getType(), VK_LValue,