At close: Fix that editors were removed even when canceling

Because the editor manager was asked first if it wants to
abort closing (because closing an editor failed), editors
were closed before any other close listener was asked.
Ask the editor manager last to avoid ending up with an
empty editor list when canceling for some other reason.

Change-Id: Ie56866cb668a717b7072d8092b4d86b7b3196d01
Task-number: QTCREATORBUG-14401
Reviewed-by: David Schulz <david.schulz@theqtcompany.com>

src/plugins/coreplugin/mainwindow.cpp

@@ -342,6 +342,7 @@ bool MainWindow::init(QString *errorMessage)
 
 void MainWindow::extensionsInitialized()
 {
+    EditorManagerPrivate::extensionsInitialized();
     MimeTypeSettings::restoreSettings();
     m_windowSupport = new WindowSupport(this, Context("Core.MainWindow"));
     m_windowSupport->setCloseActionEnabled(false);