If you are on grass path or soul sand with air to the side of it on one of the four cardinal directions, you will be pushed toward the air until you fall off the grass path/soul sand. 

This did not happen in the previous pre-release.

If there are several air blocks:
You will be pushed towards the one or two of them you are closest to.
You may be pushed towards two at once, resulting in diagonal movement.

As far as I've tested, this only affects players, not other entities.