Fix image caption mismatch

If Danbooru API returns less `image_urls` than there are `captions`, then their sizes don't match, which caused some images to get wrong captions.

app.py

@@ -142,16 +142,14 @@ class SimilaritySearcher:
         neighbours_ids = [int(x) for x in neighbours_ids]
 
         captions = []
-        for image_id, dist in zip(neighbours_ids, dists[0]):
-            captions.append(f"{image_id}/{dist:.2f}")
-
         image_urls = []
-        for image_id in neighbours_ids:
+        for image_id, dist in zip(neighbours_ids, dists[0]):
             current_url = danbooru_id_to_url(
                 image_id, selected_ratings, api_username, api_key
             )
             if current_url is not None:
                 image_urls.append(current_url)
+                captions.append(f"{image_id}/{dist:.2f}")
         return list(zip(image_urls, captions))