lua: fix NULL dereference and flawed logic

modules/lua/extension.c

@@ -1207,12 +1207,11 @@ static void WatchTimerCallback( void *data )
 
     vlc_mutex_lock( &p_ext->p_sys->command_lock );
 
-    // Do we have a pending Deactivate command?
-    if( ( p_ext->p_sys->command &&
-          p_ext->p_sys->command->i_command == CMD_DEACTIVATE )
-        || ( p_ext->p_sys->command->next
-             && p_ext->p_sys->command->next->i_command == CMD_DEACTIVATE) )
-    {
+    for( struct command_t *cmd = p_ext->p_sys->command;
+         cmd != NULL;
+         cmd = cmd->next )
+        if( cmd->i_command == CMD_DEACTIVATE )
+        {   /* We have a pending Deactivate command... */
             if( p_ext->p_sys->progress )
             {
                 dialog_ProgressDestroy( p_ext->p_sys->progress );