fixed bug in cache handling

changed files stayed in cache, but they were reported as not found,
this caused leaks and crashes
bug introduced by change of notification function,
commit 78cde69

src/exif-common.c

@@ -652,6 +652,7 @@ ExifData *exif_read_fd(FileData *fd)
 	if (!fd || !is_readable_file(fd->path)) return NULL;
 
 	if (file_cache_get(exif_cache, fd)) return fd->exif;
+	g_assert(fd->exif == NULL);
 
 	/* CACHE_TYPE_XMP_METADATA file should exist only if the metadata are
 	 * not writable directly, thus it should contain the most up-to-date version */

src/filecache.c

@@ -32,6 +32,7 @@ struct _FileCacheEntry {
 };
 
 static void file_cache_notify_cb(FileData *fd, NotifyType type, gpointer data);
+static void file_cache_remove_fd(FileCacheData *fc, FileData *fd);
 
 FileCacheData *file_cache_new(FileCacheReleaseFunc release, gulong max_size)
 {
@@ -67,9 +68,11 @@ gboolean file_cache_get(FileCacheData *fc, FileData *fd)
 			fc->list = g_list_remove_link(fc->list, work);
 			fc->list = g_list_concat(work, fc->list);
 
-			if (file_data_check_changed_files(fd)) /* this will eventually remove changed files from cache via file_cache_notify_cb */
+			if (file_data_check_changed_files(fd)) {
+				/* file has been changed, cance entry is no longer valid */
+				file_cache_remove_fd(fc, fd); 
 				return FALSE;
-				
+			}
 			if (debug_file_cache) file_cache_dump(fc);
 			return TRUE;
 			}