I am working on my final project using Google Maps to make a game, and I keep running into the same error: ide50-ssk4988.cs50.io didn’t send any data.
ERR_EMPTY_RESPONSE

This always seems to happen when I redirect to the index url using Flask's redirect and url_for functions. I have found that this only happens when the GET request is sent sing http instead of https. 

 1. Why is this happening?
 2. How do I fix it?

application.py(up until "/"):

    import os
    import re
    from flask import Flask, jsonify, render_template, request, url_for, redirect, flash, session
    from flask_session import Session
    from flask_jsglue import JSGlue
    from tempfile import mkdtemp
    from cs50 import SQL
    from helpers import *
    #credit Daniel Goldberg https://stackoverflow.com/questions/354038/how-do-i-check-if-a-string-is-a-number-float
    def is_int(value):
      try:
        int(value)
        return True
      except:
        return False
    # configure application
    app = Flask(__name__)
    JSGlue(app)
    
    # ensure responses aren't cached
    if app.config["DEBUG"]:
        @app.after_request
        def after_request(response):
            response.headers["Cache-Control"] = "no-cache, no-store, must-revalidate"
            response.headers["Expires"] = 0
            response.headers["Pragma"] = "no-cache"
            return response
    app.config["SESSION_FILE_DIR"] = mkdtemp()
    app.config["SESSION_PERMANENT"] = False
    app.config["SESSION_TYPE"] = "filesystem"
    Session(app)
    # configure CS50 Library to use SQLite database
    db = SQL("sqlite:///mashup.db")
    cities = 0
    @app.route("/")
    @login_required
    def index():
        """Render map."""
    
        if not os.environ.get("API_KEY"):
            raise RuntimeError("API_KEY not set")
        rows=db.execute("SELECT * FROM users WHERE savecode = :savecode", savecode = session["user_id"])
        rows2=db.execute("SELECT * FROM transactions WHERE savecode = :savecode", savecode = session["user_id"])
        if len(rows)==0:
            return redirect(url_for("index"))
        return render_template("index.html", key=os.environ.get("API_KEY"), cashvalue= rows[0]["cash"], cities = len(rows2))

redirect line:

    return redirect(url_for("index"))