Fixed bug in creating flashcard

Description

Fixed a bug where dictionaries were not being turned into arrays in append_items_to_array in api_error_checking because lists weren't being handled

[x] Does backend/database/database_config.py have the type of production?
[x] Does frontend/src/api/config.js have the correct server url, reading from the deployed instance at http://dolphinflashcards.com/api/?