ControllerRackView: do not loose focus when adding controller

For an unknown reason the ControllerRackView looses focus when adding
a new controller. Fix this by explicitely calling QWidget::setFocus()
at the end of ControllerRackView::addController().

Closes #3046041.
(cherry picked from commit 676a6fbad1)

src/gui/widgets/ControllerRackView.cpp

@@ -2,6 +2,7 @@
  * ControllerRackView.cpp - view for song's controllers
  *
  * Copyright (c) 2008-2009 Paul Giblock <drfaygo/at/gmail.com>
+ * Copyright (c) 2010 Tobias Doerffel <tobydox/at/users.sourceforge.net>
  *
  * This file is part of Linux MultiMedia Studio - http://lmms.sourceforge.net
  *
@@ -22,7 +23,6 @@
  *
  */
 
-
 #include <QtGui/QApplication>
 #include <QtGui/QLayout>
 #include <QtGui/QMdiSubWindow>
@@ -173,6 +173,10 @@ void ControllerRackView::addController()
 
 	engine::getSong()->addController( new LfoController( engine::getSong() ) );
 	update();
+
+	// fix bug which always made ControllerRackView loose focus when adding
+	// new controller
+	setFocus();
 }