[1.0.0] Freeze on importing malformed blueprint book

[fishtoaster]

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/wX68esk0G87WXL24ulpJ/tJxhWP14CgwTIuIIDMUhTeQ8SUGo6GUvCRmxkdwybA0gfeQcvtXQASW7b4JFaxTnRdZoy54D+WgOBTbvdUtsjIRnXHXsCaI9mqY7+VEXUtvbtCgDO5P3tn6/IkPrwyRlM4B5mzN4ypMgelOnVqu6Ef/iQ19WECzIXtDaefu9odoXuRalSncRhlWynfhql62Q==

And here's a nearly identical one that does *not* cause the issue:

0eNqFkNFqwzAMRX+l6NkpcXCS1V+wfUMpwelEMXNkY6uloeTfZ6eM5mHQN98r6ejKDxjdFUO0xMPo/Q/ox8tJoI8bWWr27OlpJ3sh44rHc0DQYBknEEBmKgrvIWJKFUdDKfjI1YiOYRFg6RvvoOVyEoDEli0+iauYB7pOI8bc8I4lIPiUxz2VFBlZqWbfCpjzS9Zq3y5lxRpLb64Q4Eyez96ndXkT774YoymcnczVG8a0MjulGnWom67tXrHr/5jV+nUCzJntDYe/1g2r+ZCqV4e+62VdeMsvUfN9yw==

The only difference is that the first one has an "index" key in the blueprint object.

I can consistently reproduce this on version 1.0.0, build 54889, mac, steam.

As an aside, I will 100% understand if this is a won't-fix. I only stumbled on this while messing around with programatically-generated blueprints. By the time I figured out what I was doing wrong, I had a simple reproduction case, though, so I figured I'd report it.

[Bilka]

Duplicate: 88307