A couple minor homing fixes

[russmatney]

Hey there! Very cool library, thanks for putting it together and open-sourcing it!

I ran into a few crashes integrating it yesterday/this morning, I thought I'd share the commit in my repo: https://github.com/russmatney/dino/commit/56fbfc2b7f95b1da8ae31737cf6085fa2151ef63.

I can create a proper PR if you want, this was just a lower-lift share, and maybe you prefer a different solution and/or can get to it sooner.

I prefer to do more things from code in general, which might explain why I hit some of these. For now I'm creating bullet and spawn patterns in an autoloaded scene, then updating and firing bullets from enemy instances this:

func fire(target):
    Spawning.change_property("bullet", "bulletPattern1", "homing_target", target.get_path())
    Spawning.change_property("bullet", "bulletPattern1", "homing_steer", 100)
    Spawning.change_property("bullet", "bulletPattern1", "homing_duration", 3)
    Spawning.spawn(self, "spawnPattern1")

This usage seems reasonable to me. It feels like the lib may expect some homing setup is expected to happen in _ready(), but it's too late if we decide afterwards that a bullet should be homing. Maybe I should just create the bullet and spawn pattern in the code as well, to resolve that?

--

I also spent a bit trying to figure out why some spawns never fired, and eventually figured out that nothing fires unless a spawner is in a positive x and y position. Moving a spawner left of the y axis or above the x axis results in no bullets at all. Maybe this is just a bug on my end? I dug into it briefly, but wasn't able to find a clear reason/solution for this yet.

Let me know what you think and if you'd like an actual PR!