[Bug] A 500 Internal Server Error occurs when an API request is made to a book without any formats.

Fixes #925

Author: crocodilestick

CONTRIBUTORS

@@ -313,7 +313,8 @@ Copyright (C) 2024-2026 Calibre-Web Automated contributors
 - zelazna (1 commits)
 - zhiyue (1 commits)
 # Fork Contributors (crocodilestick/calibre-web-automated)
-- crocodilestick (931 commits)
+
+- crocodilestick (946 commits)
 - jmarmstrong1207 (73 commits)
 - demitrix (30 commits)
 - sirwolfgang (29 commits)
@@ -337,6 +338,7 @@ Copyright (C) 2024-2026 Calibre-Web Automated contributors
 - stewie83 (3 commits)
 - zikasak (3 commits)
 - aaronpowell (2 commits)
+- BrachiumX (2 commits)
 - chad3814 (2 commits)
 - coissac (2 commits)
 - FennyFatal (2 commits)
@@ -382,6 +384,7 @@ Copyright (C) 2024-2026 Calibre-Web Automated contributors
 - jeffonthemove (1 commits)
 - jspiers (1 commits)
 - kevpam (1 commits)
+- KucharczykL (1 commits)
 - lazyusername (1 commits)
 - Lee Nave (anon) (1 commits)
 - marauder37 (1 commits)
@@ -396,6 +399,7 @@ Copyright (C) 2024-2026 Calibre-Web Automated contributors
 - rjaakke (1 commits)
 - robinwo (1 commits)
 - Rustymage (1 commits)
+- Seth Milliken (anon) (1 commits)
 - smathev (1 commits)
 - spezzino (1 commits)
 - stadler-pascal (1 commits)

cps/templates/json.txt

@@ -35,9 +35,9 @@
   "uuid": {{ entry.uuid | tojson }},
   "timestamp": {{ entry.timestamp | string | tojson }},
   "thumbnail": {{ url_for('opds.feed_get_cover', book_id=entry.id) | tojson }},
-  "main_format": {
+  "main_format": {% if entry.data.__len__() > 0 %}{
     {{ entry.data[0].format|lower | tojson }}: {{ url_for('opds.opds_download_link', book_id=entry.id, book_format=entry.data[0].format|lower) | tojson }}
-  },
+  }{% else %}{}{% endif %},
   "rating": {% if entry.ratings.__len__() > 0 %}{{ (entry.ratings[0].rating|string + ".0") | tojson }}{% else %}0.0{% endif %},
   "authors": [
   {% for author in entry.authors %}