Boats float when pushed off ledges

Replicable:

• Placing a boat and nudging it off of the block it's on causes boats to fly infinitely
• Players can enter the boat when nudged off another block but cannot drive it
• If a player enters the boat while on a fixed block they can drive it off the block and fly the boat in the air

Unreplicable:

• Boats disappear and reappear in different chunks
• Boats sometimes travel far above sky limit with rider