Fixed recursive error_handler calls (e.g. lecture page with invalid id)

server.py

-from flask import Flask, g, request, url_for, redirect, session, render_template, flash, Response
+from flask import Flask, g, request, url_for, redirect, session, render_template, flash, Response, make_response
 from werkzeug.routing import Rule
 from functools import wraps
 from datetime import date, timedelta, datetime, time, MINYEAR
@@ -162,7 +162,7 @@ def handle_errors(endpoint, text, code, *errors, **epargs):
 				return func(*args, **kwargs)
 			except errors:
 				if endpoint:
-					return render_endpoint(endpoint, text, **epargs), code
+					return make_response(render_endpoint(endpoint, text, **epargs), code)
 				else:
 					return text, code
 		return decorator