Beavers lose carried material when target stockpile set to "Empty storage"

[Withermead]

To reproduce:

Look for a beaver that's hauling from one stockpile to another. Find it's destination and set the "Empty storage" flag.

They will stop carrying to that stockpile. Sometimes they will re-target a different stockpile. Sometimes they'll just drop the material into the void and do something else.

The difference may be that Haulers will try to find a new destination but non-Hauler carriers will drop into the void. But I haven't tested that.

It seems like the re-targeting is the desired behavior.