bug#41098: Messages sent via mumi have no subject

[Ricardo Wurmus via web]

This should be fixed now.

https://git.elephly.net/gitweb.cgi?p=software/mumi.git;a=blobdiff;f=mumi/web/controller.scm;h=12065f856fc5aa350aa9b9b94b432b206c58463a;hp=d107c8d0f30bdfa9d0d8b628ffb3b9d9e6c60eaf;hb=e064812ac964bbe4f522df6a684273132ec107a2;hpb=9265dcad4929c156a635648be213956385a4e781