MacOS: kill a warning

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>
(cherry picked from commit 32b311e4109abe508fe7c17f9c32d0bb16fafa77)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/gui/macosx/AudioEffects.m

@@ -189,7 +189,7 @@ static bool GetEqualizerStatus( intf_thread_t *p_custom_intf,
 {
     vlc_object_t *p_object= VLC_OBJECT(getAout());
     if( p_object == NULL )
-        p_object = pl_Get( VLCIntf );
+        p_object = (vlc_object_t *)pl_Get( VLCIntf );
 
     if( p_object )
     {