[NFC] Avoid potential dereferencing of nullptr.

Differential Revision: https://reviews.llvm.org/D156274

Author: schittir

clang/lib/AST/ItaniumMangle.cpp

@@ -1656,6 +1656,7 @@ void CXXNameMangler::mangleUnqualifiedName(
       // Otherwise, use the complete destructor name. This is relevant if a
       // class with a destructor is declared within a destructor.
       mangleCXXDtorType(Dtor_Complete);
+    assert(ND);
     writeAbiTags(ND, AdditionalAbiTags);
     break;
 

clang/lib/Sema/SemaCodeComplete.cpp

@@ -6601,7 +6601,7 @@ void Sema::CodeCompleteQualifiedId(Scope *S, CXXScopeSpec &SS,
   // The "template" keyword can follow "::" in the grammar, but only
   // put it into the grammar if the nested-name-specifier is dependent.
   // FIXME: results is always empty, this appears to be dead.
-  if (!Results.empty() && NNS->isDependent())
+  if (!Results.empty() && NNS && NNS->isDependent())
     Results.AddResult("template");
 
   // If the scope is a concept-constrained type parameter, infer nested