Clang: Highlight invalid declarations as text

...instead of the corresponding declaration color.

Task-number: QTCREATORBUG-18686
Change-Id: Ice4d84816351af79efa286f49516c392bd80da86
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

src/tools/clangbackend/source/tokeninfo.cpp

@@ -308,6 +308,9 @@ void TokenInfo::identifierKind(const Cursor &cursor, Recursion recursion)
 {
     m_isIdentifier = (cursor.kind() != CXCursor_PreprocessingDirective);
 
+    if (cursor.isInvalidDeclaration())
+        return;
+
     switch (cursor.kind()) {
         case CXCursor_Destructor:
         case CXCursor_Constructor: