The bug

In ItemGlassBottle.java (MCP name) the Radius of the dragon breath cloud gets decremented by 0.5 for every right-click.
The clouds from the purple fireballs vanish when the size is 0, but the clouds from the dragon when he is in the middle vanish after time.
Even when the clouds radius is less than 0 the cloud stays there.
Visually the negative sized cloud starts to grow again with every right-click.

Video: https://youtu.be/QLzV25kjl3Y

What I expected to happen was...

If there is not enough cloud left, i would not be able to fill the bottle.

What actually happened was...

Cloud grows bigger.

Steps to reproduce

1. Summon an enderdragon with a custom UUID

   /summon ender_dragon ~ ~ ~ {NoAI:1b,UUIDLeast:0L,UUIDMost:0L}
   

2. Summon an area effect cloud with the ender dragon as owner

   /summon area_effect_cloud ~ ~ ~ {Duration:2000,Radius:5f}
   

3. Start right clicking the area effect cloud with glass bottles
   → The cloud will shrink, then grow again and vanish after some time