exec's "<&" Bug

If these three lines are entered into the terminal after a "inventory.txt" file is established:

FILE=inventory.txt
exec 6<&0
exec 0<$FILE

The terminal crashes (closes completely) after the last line is entered. Could this be a bug? The programmer never gets to use the redirect or even restore stdin to file descriptor "0" or to close the file descriptor.
Or perhaps I could be doing something wrong.

If it is a bug, it looks like a big one.