CppEditor: Fix nullptr access

...for invalid code.

Task-number: QTCREATORBUG-18355
Change-Id: If5d4d90a7dbaa770008e4e6c54c7ff3a86c6da89
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

src/plugins/cppeditor/cppinsertvirtualmethods.cpp

@@ -591,7 +591,8 @@ public:
             for (Scope::iterator it = clazz->memberBegin(); it != clazz->memberEnd(); ++it) {
                 if (const Function *func = (*it)->type()->asFunctionType()) {
                     // Filter virtual destructors
-                    if (func->name()->asDestructorNameId())
+                    const Name *name = func->name();
+                    if (!name || name->asDestructorNameId())
                         continue;
 
                     const Function *firstVirtual = 0;