CppEditor: Check for canceled future

Task-number: QTCREATORBUG-18793
Change-Id: I80a811814e5c7edc1e9b94ed0775abfc21723da2
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/cppeditor/cppuseselectionsupdater.cpp

@@ -98,6 +98,8 @@ void CppUseSelectionsUpdater::update(CallType callType)
 
         const int startRevision = cppEditorDocument->document()->revision();
         QFuture<CursorInfo> future = cppEditorDocument->cursorInfo(params);
+        if (future.isCanceled())
+            return;
 
         // QFuture::waitForFinished seems to block completely, not even
         // allowing to process events from QLocalSocket.