Return 404 instead 500 when plugin is disabled.

app/controllers/application_controller.rb

@@ -94,7 +94,9 @@ class ApplicationController < ActionController::Base
     end
   end
 
-  rescue_from Discourse::NotFound do
+  class PluginDisabled < StandardError; end
+
+  rescue_from Discourse::NotFound, PluginDisabled do
     rescue_discourse_actions(:not_found, 404)
   end
 
@@ -120,8 +122,6 @@ class ApplicationController < ActionController::Base
     end
   end
 
-  class PluginDisabled < StandardError; end
-
   # If a controller requires a plugin, it will raise an exception if that plugin is
   # disabled. This allows plugins to be disabled programatically.
   def self.requires_plugin(plugin_name)