Trying to use item on mob leashed to yourself always clears leash first

The bug

When you try to use an item, like a name tag or a spawn egg, on a mob leashed to yourself the leash is always cleared. Expected would be that the leash is either only cleared when you are not holding an item or when the item cannot be used on the mob (EnumActionResult.PASS).

How to reproduce

1. Leash a pig
2. Try right clicking the pig with a pig spawn egg to spawn baby pigs
   → The leash is cleared