Ender Dragon takes no damage from Warden

Steps to Reproduce:

1. Summon warden and ender dragon

2. Run the command to have Warden attacks Ender Dragon: /damage @e[type=warden] 0 entity_attack entity @e[type=ender_dragon,c=1]

3. Observe

Expected Results:
Ender dragon should get damaged by the warden's attacks

Observed Results:
Ender dragon doesn't receive any damage from the warden's attacks

Video:
https://drive.google.com/file/d/1y-XRot9OmpkQycZYagJE-wQhXl5_p_5u/view?usp=sharing