Fix crash when lambda is null

Author: ganenkokb-yandex

clang/lib/AST/ASTStructuralEquivalence.cpp

@@ -1609,6 +1609,12 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
 static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                      CXXMethodDecl *Method1,
                                      CXXMethodDecl *Method2) {
+  if (!Method1 && !Method2) {
+    return true;
+  }
+  if (!Method1 || !Method2) {
+    return false;
+  }
   bool PropertiesEqual =
       Method1->getDeclKind() == Method2->getDeclKind() &&
       Method1->getRefQualifier() == Method2->getRefQualifier() &&