tools/batch-rebase: Fix handling of empty commits at topic boundaries
tools/batch-rebase: Fix handling of empty commits at topic boundaries

Avoid an infinite loop when a cherry pick would lead to an empty commit at the
boundary of the cherry-picked range.

credp/lisa,credp/lisa,ARM-software/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa