${var+set}, ${var:+nonempty} broken in current git

[Martijn Dekker]

Commit 3cd538634f71538370f5af239f342aec48b7470b broke these:

$ src/dash -c 'unset var; echo ${var+set}'
set
$ src/dash -c 'var=; echo ${var:+nonempty}'
nonempty

HTH,

- M.