Qt4: don't keep reference to toAscii() temporary array

(See also previous commit)
(cherry picked from commit cf190075bda0c39e2a203104d9095c450e283def)

modules/gui/qt4/components/extended_panels.cpp

@@ -1026,13 +1026,12 @@ void Equalizer::setCoreBands()
         band_texts[i]->setText( band_frequencies[i] + "\n" + val + "dB" );
         values += " " + val;
     }
-    const char *psz_values = values.toAscii().constData();
 
     aout_instance_t *p_aout = THEMIM->getAout();
     if( p_aout )
     {
         //delCallbacks( p_aout );
-        var_SetString( p_aout, "equalizer-bands", psz_values );
+        var_SetString( p_aout, "equalizer-bands", qtu( values ) );
         //addCallbacks( p_aout );
         vlc_object_release( p_aout );
     }