qt4: fix a crash if "view-mode" configuration values are invalid.

(cherry picked from commit ef2ea798)
Signed-off-by: Rémi Duraffort <ivoire@videolan.org>

modules/gui/qt4/components/playlist/standardpanel.cpp

@@ -125,6 +125,9 @@ StandardPLPanel::StandardPLPanel( PlaylistWidget *_parent,
     int i_viewMode = getSettings()->value( "view-mode", TREE_VIEW ).toInt();
 
     getSettings()->endGroup();
+    /* Limit the saved value to a possible one inside [0, VIEW_COUNT[ */
+    if(i_viewMode < 0 || i_viewMode >= VIEW_COUNT)
+        i_viewMode = 0;
 
     showView( i_viewMode );