Minecart detaches from a rail too early

The bug

Rails don't extend all the way to the edge of a block; When the center of a minecart is not above a rail, the minecart behaves as it's not on a rail, even though it's hitbox is above. This causes it to fall through a rail; if it was slow enough - on the block below.

How to reproduce

1. Put 3-7 normal rails in a line.
2. On one of the ends of the line put a powered rail, then a block with a button on it (so it blocks this end).
3. On the other end dig a pit for a minecart to fall.
4. Put a minecart on the powered rail.
5. Push the button.
   → The minecart will ride to the other end and descend, falling onto the ending block, not into the pit next to it.