Qt4: restart the playlist in the correct state when closed

Close #3788
(cherry picked from commit 3d80127ebdfc7d73b4ee3af2230e1d74e11adb3d)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

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

@@ -151,7 +151,7 @@ void PlaylistWidget::closeEvent( QCloseEvent *event )
 {
     if( THEDP->isDying() )
     {
-        /* FIXME is it needed ? */
+        p_intf->p_sys->p_mi->playlistVisible = true;
         event->accept();
     }
     else

modules/gui/qt4/main_interface.cpp

@@ -286,12 +286,7 @@ MainInterface::~MainInterface()
     settings->setValue( "pl-dock-status", b_plDocked );
     /* Save playlist state */
     if( playlistWidget )
-    {
-        settings->setValue( "playlist-visible",
-                            isPlDocked() ?
-                            playlistVisible :
-                            playlistWidget->isVisible() /* FIXME */ );
-    }
+        settings->setValue( "playlist-visible", playlistVisible );
 
     settings->setValue( "adv-controls",
                         getControlsVisibilityStatus() & CONTROLS_ADVANCED );