macosx: save volume in prefs only if controls are editable

Signed-off-by: Felix Paul Kühne <fkuehne@videolan.org>
(cherry picked from commit 53b2dfec)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/macosx/simple_prefs.m

@@ -855,7 +855,8 @@ static inline void save_module_list( intf_thread_t * p_intf, id object, const ch
     if( b_audioSettingChanged )
     {
         config_PutInt( p_intf, "audio", [o_audio_enable_ckb state] );
-        config_PutInt( p_intf, "volume", [o_audio_vol_fld intValue] * AOUT_VOLUME_MAX / 200 );
+        if( [o_audio_vol_fld isEnabled] )
+            config_PutInt( p_intf, "volume", [o_audio_vol_fld intValue] * AOUT_VOLUME_MAX / 200 );
         config_PutInt( p_intf, "macosx-autosave-volume", [o_audio_autosavevol_yes_bcell state] );
         config_PutInt( p_intf, "spdif", [o_audio_spdif_ckb state] );