Reloading a world while in or ungrounded above lava will place the player at the next available platform

If the player is in or ungrounded (i.e, flying or falling) above still or flowing lava when a world is reloaded, they will be placed on any platform of solid blocks higher than both their previous location and the lava. If there isn't any block above the lava to be set upon, the player will be teleported to the world spawn point and sent the client message "Your home bed was missing or obstructed".
Tested in Creative and Survival mode, additional testing by @rplatham on Samsung Galaxy S4 (Android 5.0.1). This is a big problem in the Nether, where it can result in the player becoming stranded on top of the bedrock roof.