Problems with team_id being empty

[thorgrin]

I've recently pushed a fix for links to files which handles team_id being an empty string. However, it is probably a bigger problem as stated by

		//FIXME: in v4 api team_id is NULL for group chats, that breaks the code in many places.
		//       should be rewritten.

		//if (team_id == NULL || strlen(team_id) == 0) {
		//	team_id = mm_get_first_team_id(ma);
		//}

What would happen when we added this check whenever ma->channel_teams is written to? I've tried it and it solved my problem at a root, but there are probably side effects which I cannot see.