TextEditor: Fixes crash when double clicking virtual function proposal

Ensures that the DeferredDelete event is posted from the outermost
loop level.

Change-Id: Ib74d49d35811f35659ef272d6f0e0a4508f93076
Reviewed-by: David Schulz <david.schulz@theqtcompany.com>

src/plugins/texteditor/codeassist/genericproposalwidget.cpp

@@ -440,9 +440,9 @@ void GenericProposalWidget::notifyActivation(int index)
 
 void GenericProposalWidget::abort()
 {
+    deleteLater();
     if (isVisible())
         close();
-    deleteLater();
 }
 
 bool GenericProposalWidget::updateAndCheck(const QString &prefix)