thumbnail view: Search for collection link if requested

- uses one found, if only one was found to prevent issues when multiple
would be possible

server/app.py

@@ -21,6 +21,7 @@ from typing import (
     List,
     Mapping,
     Optional,
+    Sequence,
     Set,
     Type,
     TypeVar,
@@ -246,6 +247,11 @@ def encode_options(opts: Mapping[str, Any]) -> str:
     return urlencode({k: str(v) for k, v in opts.items()}, quote_via=quote_plus)
 
 
+@flask_app.template_filter()
+def first_and_only(list: Sequence[T]) -> Optional[T]:
+    return list[0] if len(list) == 1 else None
+
+
 @flask_app.template_global()
 def this_url(changed_args: Mapping[str, str] = {}) -> str:
     if request.endpoint is None:

server/templates/macros.htm

@@ -388,6 +388,9 @@
                 alt="Thumbnail for {{ element.title }}"
                 loading="lazy"
             />
+            {% if link == None %}
+                {% set link = element.detected_playlists | list | first_and_only %}
+            {% endif %}
             {% if link and (link.season or link.episode) %}
                 <a
                     class="episode_info"