Free the end Advancement Ender Dragon Glitch

Put the summary of the bug you're having here

What I expected to happen was...: When i killed the dragon i espected to get free the end

What actually happened was...: I did not get the advancement and when i got the dragon egg and the advancement "The next generation" the advancement tab skippe dfree the end which makes it look like a bug.

Steps to Reproduce:
1. Kill the Ender dragon with bed explosion damage
2. Avoid the Free the end advancement even though you Free'd the end.