git-send-email: fix missing space in error message

When the command cannot make a connection to the SMTP server the error
message to diagnose the broken configuration is issued.  However, when an
optional smtp-server-port is given and needs to be reported, the message
lacked a space between "hello=<smtp-domain>" and "port=<smtp-server-port>".

Signed-off-by: Sylvain Rabot <sylvain@abstraction.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-send-email.perl

@@ -1091,7 +1091,7 @@ sub send_message {
 			    "VALUES: server=$smtp_server ",
 			    "encryption=$smtp_encryption ",
 			    "hello=$smtp_domain",
-			    defined $smtp_server_port ? "port=$smtp_server_port" : "";
+			    defined $smtp_server_port ? " port=$smtp_server_port" : "";
 		}
 
 		if (defined $smtp_authuser) {