Mail: Avoid showing contacts' empty addresses

Other contacts apps like Peeps! allow for more than one email
addresses, using the attributes META:email{n} with n >=2.
Only, not all contacts having those additional attributes have
them actually filled.

This results duplicate entries in e.g. the To-field pop-up with
no email address attached.

We now only add an item if its email address isn't empty for those
additional email attributes as well.

Change-Id: Icb1750fe8e2b10280bc01b3181b444f01096e021
Reviewed-on: https://review.haiku-os.org/c/haiku/+/9329
Tested-by: Commit checker robot <[email protected]>
Reviewed-by: waddlesplash <[email protected]>

src/apps/mail/People.cpp

@@ -36,7 +36,7 @@ AddPersonAddresses(BNode& node, BStringList& addresses)
 		char attr[32];
 		snprintf(attr, sizeof(attr), "META:email%d", i);
 
-		if (node.ReadAttrString(attr, &email) != B_OK)
+		if (node.ReadAttrString(attr, &email) != B_OK || email.IsEmpty())
 			break;
 
 		addresses.Add(email);