Clang: Fix warning in HighlightingMark::punctuationKind

Actually mixing returns and not is not that well readable workflow. A other
option would be to use if.

Change-Id: I36f07adb77d50ddc6890b6292c7883a1b5f80f58
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/tools/clangbackend/ipcsource/highlightingmark.cpp

@@ -374,12 +374,16 @@ HighlightingType operatorKind(const Cursor &cursor)
 
 HighlightingType HighlightingMark::punctuationKind(const Cursor &cursor)
 {
+    HighlightingType highlightingType = HighlightingType::Invalid;
+
     switch (cursor.kind()) {
-        case CXCursor_DeclRefExpr: return operatorKind(cursor);
+        case CXCursor_DeclRefExpr: highlightingType = operatorKind(cursor); break;
         case CXCursor_Constructor:
-        case CXCursor_CallExpr:    collectOutputArguments(cursor);
-        default:                   return HighlightingType::Invalid;
+        case CXCursor_CallExpr:    collectOutputArguments(cursor); break;
+        default:                   break;
     }
+
+    return highlightingType;
 }
 
 static HighlightingType highlightingTypeForKeyword(CXTranslationUnit cxTranslationUnit,