Specify a default for all site settings

config/settings.yml

@@ -39,6 +39,7 @@ plugins:
   chat_integration_telegram_enable_slash_commands:
     default: true
   chat_integration_telegram_secret:
+    default: ''
     hidden: true
 
 #######################################
@@ -83,4 +84,4 @@ plugins:
   chat_integration_matrix_access_token:
     default: ''
   chat_integration_matrix_excerpt_length:
-    default: 400
+    default: 400