DEV: correct intermittent test failure

ActionController::BadRequest can not be re-dispatched, under some conditions
we are getting this vs InvalidParameterError in the following test

59c56bd20f/spec/requests/application_controller_spec.rb (L34-L62)

lib/middleware/discourse_public_exceptions.rb

@@ -20,6 +20,9 @@ module Middleware
       # the Request object has a "broken" .params which can not be accessed
       exception = nil if Rack::QueryParser::InvalidParameterError === exception
 
+      # We also can not dispatch bad requests as no proper params
+      exception = nil if ActionController::BadRequest === exception
+
       if exception
         begin
           fake_controller = ApplicationController.new