use "" as an array key

[Matt Maier]

I find myself in want of a YAML library again. Mark posted some functions
on the forum that I'm debugging
http://forums.livecode.com/viewtopic.php?f=7&t=21434

Something I discovered while debugging is that "" is being accepted as an
array key.

It seems like it shouldn't be possible to use the absence of a string as an
array key. Is it supposed to work that way? I'm using 8.0.1 on Windows.