I...genuinely have no idea what's going on with this error. I've tested this myself and it's worked fine for me. Sadly there's nothing I can really glean from the error that's been thrown here either. The best I could gather is that it's tried to run script used for the attacking timer, since it has the illegal time source thing here. But it shouldn't be doing that with Selvata at any point, and it's somehow throwing the line -1 as the one causing the issue which is just...what? There isn't a line -1.
Really sorry that I can't help with this. If anyone else knows Gamemaker language that can figure out what's the problem here I'm glad to do what I can to fix it though.