nested reaction tasks patch

What does this MR do and why?

Fix bug where nested reaction tasks would stack

We were setting next runtime of tasks (reactions) that we could not calculate the runtime for.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• Have you checked this doesn't interfere/conflict/duplicate someone elses work?
• Have you fully tested your changes?
• Have you resolved any lint issues?
• Have you assigned a reviewer?
• Have you applied correct labels?