a 0-card deck error fixed

menu.py

@@ -1,5 +1,5 @@
 from flask import (
-    Blueprint, redirect, render_template, request, session, url_for
+    Blueprint, flash, redirect, render_template, request, session, url_for
 )
 
 from config import CONFIG 
@@ -48,10 +48,11 @@ def index():
                 #ustvari novi vnos v Deck
                 user_settings = get_settings(user_id)
                 deck = probabilistic_deck_generator(user_id, int(user_settings['max_new']), int(user_settings['max_due']))
+
                 cards_by_id = get_deck(deck)
-                if cards_by_id == None:
-                    print("Deck is none")
-                    return render_template(index())
+                if cards_by_id == "":
+                    flash("Error: Attempted to make deck with 0 cards. Maybe check settings :)")
+                    return render_template("menu/menu.html")
                 else:
                     number_of_cards = len(cards_by_id.split(","))