Removing an elytra mid-flight does not reset the player's hitbox

*Partner Rank:*

2

*Partner Team Reporting:*

Everbloom Studios

*Verification builds:*

beta 1.11.0.10 (Release_2012206) and beta 1.12.0.3 (Release_2120526) on Windows 10

*Summary:*

When an elytra is taken from the player while they are in the flying animation, the player's hitbox sometimes isn't reset to its normal state. This results in the player being able to walk through 1-block-tall spaces. Note that this happens even when the elytra is removed using the /clear command or /replaceitem.

The collision box seems to fix itself after relogging, diving in water or deploying the elytra again.

*Impact:*

Players with an elytra can easily manipulate their hitbox to fit through 1-block-tall spaces they're not supposed to access, even after the elytra is cleared from their inventory.

*Repro Steps:*

1. Join a world, equip an elytra and put yourself on a high place.
2. Drop down, deploy the elytra
3. In mid-air, while gliding and before landing, remove your elytra (can be through the inventory, /clear or /replaceitem)

*Observed Results:*

After landing, you are able to walk through 1-block-tall spaces and clip into ceilings, as long as you don't relog, swim in water or re-deploy elytra wings.
(This may not always happen, so be sure to try it multiple times if it doesn't immediately work)

*Expected Results:*

The player's hitbox should reset after landing, whether they have an elytra or not.

*Screenshots/Videos attached: Yes/No*

Yes

*Regression Builds:*

Unknown

*Notes:*

Video (exceeded maximum file size, so here it is on YouTube)