playlist.c: shut up a compiler warning

item-ext.c: reverted a recent change in GetPositionById than caused
old-style playlist to malfunction (visible in rc interface at least)

src/playlist/item-ext.c

@@ -387,9 +387,9 @@ int playlist_NodeAddItem( playlist_t *p_playlist, playlist_item_t *p_item,
 int playlist_GetPositionById( playlist_t * p_playlist , int i_id )
 {
     int i;
-    for( i =  0 ; i < p_playlist->i_all_size ; i++ )
+    for( i =  0 ; i < p_playlist->i_size ; i++ )
     {
-        if( p_playlist->pp_all_items[i]->input.i_id == i_id )
+        if( p_playlist->pp_items[i]->input.i_id == i_id )
         {
             return i;
         }

src/playlist/playlist.c

@@ -482,7 +482,7 @@ static mtime_t ObjectGarbageCollector( playlist_t *p_playlist, int i_type,
 static void RunThread ( playlist_t *p_playlist )
 {
     vlc_object_t *p_obj;
-    playlist_item_t *p_item;
+    playlist_item_t *p_item = NULL;
 
     mtime_t    i_vout_destroyed_date = 0;
     mtime_t    i_sout_destroyed_date = 0;