Fix messages with blank bodies not showing up on iphone

As reported by Keyop, messages with a blank body would not show up on the iphone email client when using imap. This will insert a fake body if none exists.

assigned to @rswindell

Checking out 83cfb5a0 as detached HEAD (ref is fix_blank_imap_body)... ERROR: Job failed: execution took longer than 1h0m0s seconds

Not my fault if NetBSD can't build scfg. Someone needs to fix that.

mentioned in commit 60e75edb

merged