When importing a blueprint book string, if the `blueprint_book.blueprints[0].index` key is missing, the game immediately becomes unresponsive and must be force quit.

Here's a blueprint string that causes the issue:

0eNqFkN1qwzAMhV+l6NopcXCS1U/QPcMYwenEMHNkY6uloeTdZ7uD5WKwO50j6dPPA2Z3xRAt8TR7 ...