This most likely wouldn't be safe for poison ivy removal. Burning poison ivy creates a toxic cloud. As much as poison ivy isn't fun, poison ivy in your throat and lungs is even less fun.
You need to think more "hit it with enough energy to break cell walls and kill the weed" and not "burn it in fire like a SciFi movie.
The robot has nobody near it. Toxic clouds would burn with no ill effect to humans.
Presumably the laser wouldn't be setting the whole plant up in smoke. Couldn't it target the base and let it fall?
My understanding of poison ivy is that no part of the plant is nontoxic. Burning just the base would minimize the toxic cloud, but not eliminate it.
I really don't think that burning a line an inch long and 1/16th of an inch thick at the bottom of a stem is going to release any significant amount of toxic cloud. A tiny bit if you're right there next to it, sure, but it would be dissipated within a few minutes.