Can`t shift click in horse inventory.

Put the summary of the bug you're having here

What I expected to happen was...: - I was on my horse and could only shift click the saddle but not other items in the inventory.
Describe what you thought should happen here - I thought you could shift click other items.

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. get a tammed horse and other items
3. put saddle on and try to shift click items around.