"minecraft.custom:minecraft.damage_dealt" doesn't increase when damaging the ender dragon

The Bug:

"minecraft.custom:minecraft.damage_dealt" doesn't increase when damaging the ender dragon.

Please note that you must attack the ender dragon using a melee source of damage as a result of MC-29519.

Steps to Reproduce:

1. Create a scoreboard objective for tracking when you deal damage and set it to display on the sidebar by using the commands provided below. 

   /scoreboard objectives add DamageDealt minecraft.custom:minecraft.damage_dealt

   /scoreboard objectives setdisplay sidebar DamageDealt

2. Summon an ender dragon and attack it.
3. Take note as to whether or not "minecraft.custom:minecraft.damage_dealt" increases when damaging the ender dragon.

Observed Behavior:

The scoreboard doesn't increase.

Expected Behavior:

The scoreboard would increase.