CppEditor: Assign parent to "Extract Function" dialog

Change-Id: I37bdafe640cca00211f1c558f2f2afc5d12d8357
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>

src/plugins/cppeditor/cppquickfixes.cpp

@@ -3336,7 +3336,7 @@ public:
 
     ExtractFunctionOptions getOptions() const
     {
-        QDialog dlg;
+        QDialog dlg(Core::ICore::dialogParent());
         dlg.setWindowTitle(QCoreApplication::translate("QuickFix::ExtractFunction",
                                                        "Extract Function Refactoring"));
         auto layout = new QFormLayout(&dlg);