Burning arrows in ground are not extinguished by rain

The bug

Burning arrows in ground are not extinguished by rain.

How to reproduce

1. Shoot an arrow with a flame bow
2. /toggledownfall when it is already in the ground
3. The arrow will not be put out of its fire
4. Break the block that the arrow is stuck to
5. The arrow is extinguished

Code analysis

Code analysis by Marcono1234 can be found in this comment.