subtitles: Fix "any subtitle" detection.

(cherry picked from commit 2ae88e92)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

src/input/subtitles.c

@@ -360,7 +360,7 @@ char **subtitles_Detect( input_thread_t *p_this, char *psz_path,
                 }
             }
             else if( i_prio == SUB_PRIORITY_NONE &&
-                j == 0 )
+                j == -1 )
             {
                 /* doesn't contain the movie name, prefer files in f_dir over subdirs */
                 i_prio = SUB_PRIORITY_MATCH_NONE;