I am getting an error in simplejson in python

Question

my code

import simplejson as json
import os
if os.path.isfile("./ages.json") and os.stat("./ages.json") != 0:
    old_file = open("./ages.json","r+")
    data = json.loads(old_file.read())
    print("Current age is ", data["age"])
    data[0]["age"] = data[0]["age"] + 1
    print("New age ",data[0]["age"])
else:
    old_file = open("./ages.json","w+")
    data = {"Name":"nick","age":14}

    print("No age detacted .setting default age to",data[0]["age"])
old_file.seek(0)
old_file.write(json.dumps(data))

error-

simplejson.errors.JSONDecodeError: Expecting value: line 1 column 1 (char 0)