Fire Damage cancels out Fall Damage

So I was in The Nether trying to make a bridge, and a ghast blasts a fireball at me, I get caught on fire and get knocked off. I expect my death, but instead, the fire damage does some damage as soon as I was about to fall, canceling out the fall damage entirely. And yes, fall damage is set to true.

 

I also have a video of the bug in action: https://www.youtube.com/watch?v=dNRmDoXozNk