Fix edge case where invalid theme_settings cause broken frontend (#2034)

* Fix edge case where invalid `theme_settings` cause broken frontend

CTFd/constants/config.py

@@ -76,7 +76,10 @@ class _ConfigsWrapper:
 
     @property
     def theme_settings(self):
-        return json.loads(get_config("theme_settings", default="null"))
+        try:
+            return json.loads(get_config("theme_settings", default="null"))
+        except json.JSONDecodeError:
+            return {"error": "invalid theme_settings"}
 
     @property
     def tos_or_privacy(self):

CTFd/themes/admin/assets/js/pages/configs.js

@@ -410,6 +410,7 @@ $(() => {
     {
       lineNumbers: true,
       lineWrapping: true,
+      readOnly: true,
       mode: { name: "javascript", json: true }
     }
   );