media_cache: Mark cache entry stale if cache file is removed

In the event that a cache file is removed out from under us, we should
treat the cache entry as stale and force a refresh.

ASTERISK-26774 #close
Reported by: Igor Gamayunov

Change-Id: I3b1bd0c999d59d18664ef73a29823bc5b431dc52

main/media_cache.c

@@ -226,7 +226,8 @@ int ast_media_cache_retrieve(const char *uri, const char *preferred_file_name,
 	 */
 	bucket_file = ao2_find(media_cache, uri, OBJ_SEARCH_KEY | OBJ_NOLOCK);
 	if (bucket_file) {
-		if (!ast_bucket_file_is_stale(bucket_file)) {
+		if (!ast_bucket_file_is_stale(bucket_file)
+			&& !access(bucket_file->path, R_OK)) {
 			ast_copy_string(file_path, bucket_file->path, len);
 			if ((ext = strrchr(file_path, '.'))) {
 				*ext = '\0';