Non-player mobs should not get into driver's seat of boat

Mobs should not be allowed to enter the front seat of a boat.

It is a feature that a mob can ride as a passenger in a boat so the player can drive them around. However, it seems like an unintended feature that two mobs are able to get into the same boat. The front seat of a boat should be exclusively reserved for player characters. This is particularly noticeable with turtles, where a docked boat next to a beach has a very high chance of getting one or even two turtles to randomly enter the boat.