Qt4: never assign qtu() to a variable

As far as I understand, this breaks C++ object scoping. qtu() creates
a temporary anonymous QByteArray from its QString parameter. That array
is destroyed at the end of the expression, thus the return value of
qtu() becomes a dangling pointer.
(cherry picked from commit 41c3dd9b229c44cb313786f96cc2089a9d5197cc)

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

@@ -883,9 +883,8 @@ void PLModel::search( const QString& search_text, const QModelIndex & idx, bool
         playlist_item_t *p_root = playlist_ItemGetById( p_playlist,
                                                         itemId( idx ) );
         assert( p_root );
-        const char *psz_name = qtu( search_text );
-        playlist_LiveSearchUpdate( p_playlist , p_root, psz_name, b_recursive );
-
+        playlist_LiveSearchUpdate( p_playlist , p_root, qtu( search_text ),
+                                   b_recursive );
         if( idx.isValid() )
         {
             PLItem *searchRoot = getItem( idx );