What steps will reproduce the problem?
1. log in a druid
2. heal self with Rejuvenation or Regrowth
3. as the heal over time effect is about to end, the add-on crashes

What is the expected output? What do you see instead?

What version of the product are you using?

2.4.2.2

Do you have an error log of what happened?

Interface\Addons\Healbot\Healbot.lua 2284: attept to perform arithmetic on upvalue 'x' (a nil value)

Please provide any additional information below.

Getting the error when I use my druid heal over time spells. It looks like the code is trying to do something with Swiftmend, but I am not specced with Swiftmend.