Don't loose composition window when opening mail
Don't loose composition window when opening mail

Steps to reproduce:
 * open message in popup window
 * click reply or forward
 * re-open message in popup window from the messages list

It will now open the message in a separate popup.

Fixes #1908.

Distrotech/sogo,Distrotech/sogo,Distrotech/sogo,Distrotech/sogo,Distrotech/sogo