Deleting the last key by negative index does not work; deleting keys by value deletes all of them

[JonnyOThan]

Possibly related to #75?

Given a node like:

THING
{
  transform = airlock
  transform = airlockTopB
}

and a patch targeting that node,

-transform,-1 = delete does nothing -transform[airlockTopB] = delete deletes all of them -transform,1 = delete seems to work, but of course it's super fragile