Capes clip through the player when taking knockback

The Bug

Capes equipped by the player can go through the back of the player when taking knockback (e.g. from a Wind Charge or creeper explosion).

This is much more apparent when crouching and getting knocked back.

Steps to Reproduce

1. Ensure you have a cape equipped.
2. Go into third-person mode by pressing F5 once.
3. While crouching, shoot a Wind Charge at your feet.

Observed Results

The cape goes through the player's body.

Expected Results

The cape moves with the player's body while taking knockback.