DEV: better log around nil client_settings_json (#27868)

Internal ref t/132507

lib/site_setting_extension.rb

@@ -154,33 +154,36 @@ module SiteSettingExtension
   end
 
   def client_settings_json
-    Discourse
-      .cache
-      .fetch(SiteSettingExtension.client_settings_cache_key, expires_in: 30.minutes) do
-        client_settings_json_uncached
-      end
+    key = SiteSettingExtension.client_settings_cache_key
+    json = Discourse.cache.fetch(key, expires_in: 30.minutes) { client_settings_json_uncached }
+    Rails.logger.error("Nil client_settings_json from the cache for '#{key}'") if json.nil?
+    json || ""
+  rescue => e
+    Rails.logger.error("Error while retrieving client_settings_json: #{e.message}")
+    ""
   end
 
   def client_settings_json_uncached
     MultiJson.dump(
       Hash[
-        *@client_settings
-          .map do |name|
-            value =
-              if deprecated_settings.include?(name.to_s)
-                public_send(name, warn: false)
-              else
-                public_send(name)
-              end
-            type = type_supervisor.get_type(name)
-            value = value.to_s if type == :upload
-            value = value.map(&:to_s).join("|") if type == :uploaded_image_list
+        *@client_settings.flat_map do |name|
+          value =
+            if deprecated_settings.include?(name.to_s)
+              public_send(name, warn: false)
+            else
+              public_send(name)
+            end
+          type = type_supervisor.get_type(name)
+          value = value.to_s if type == :upload
+          value = value.map(&:to_s).join("|") if type == :uploaded_image_list
 
-            [name, value]
-          end
-          .flatten
+          [name, value]
+        end
       ],
     )
+  rescue => e
+    Rails.logger.error("Error while generating client_settings_json_uncached: #{e.message}")
+    nil
   end
 
   # Retrieve all settings