BUG: Fix empty parentheses in Send Later header in preview window
BUG: Fix empty parentheses in Send Later header in preview window

Fix a bug introduced in release 6.0.4beta2 with empty parentheses
displaying in the X-Send-Later-At header when viewing a draft in the
message preview window.

jikamens/send-later,jikamens/send-later,jikamens/send-later,jikamens/send-later