Comets have VFX error on spawn

[Starstrider42]

Description

When a comet is created using Custom Asteroids, the log emits [ProtoVessel]: Unable to create Comet VFX. immediately afterward. The comet does not show a coma and tail in the tracking station until at least one scene change since the comet appeared. Track down the error and ensure that comets are correctly displayed right away.

To Reproduce
Steps to reproduce the behavior:

1. Load KSP with a Custom Asteroids config that supports comets.
2. Start a new default game, and enter the tracking station.
3. Time warp until a comet appears, and track it.
4. Verify the error message in the Alt+F12 console.
5. Time warp until the comet gets within Kerbin's orbit.
6. Zoom in and verify that no visual effects are present.
7. Leave and re-enter the tracking station.
8. Time warp slightly, a second of 5× is enough.
9. Zoom in on the comet and verify that it has a tail.

Background Info

• Operating System: Windows 10 64-bit
• KSP Version: 1.10.0
• Custom Asteroids Version: development build of 1.9
• Other mods: none