minor "enter" annoyance

[Tripp Lilley]

If I start to enter a transaction, but don't yet have any split rows (just
the date and transaction name / note), and I hit <enter> instead of <tab>,
the transaction goes away.

I know that <enter> means "commit this transaction", but perhaps it could
mean "commit this transaction if it's non-empty and balanced, otherwise
show a balance dialog if it's non-empty and unbalanced, or act like <tab>
if it's empty"