Patch PB bonus projectile knockback

[Doubleumc]

About the pull request

Prevents an issue with PB bonus projectiles.

In a PB, the initial projectile is never "fired", it remains in nullspace. That's fine, since there's special handling in knockback code for a projectile in nullspace, it uses the firer.

In a PB, bonus projectiles are set to the target's loc. That doesn't matter much except for knockback, which uses the position of the projectile vs. the position of the target. The bonus projectile is on the same tile as the target, so it can't give a sane angle, so it defaults to EAST.

This changes the bonus projectile's position to nullspace, matching how the initial projectile works.

Explain why it's good for the game

If a bonus projectile with knockback were ever to be used, this will prevent issues.

Testing Photographs and Procedure

Screenshots & Videos

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Changelog

No player facing changes.

[github-actions]

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