More robust guest members for users and tests for it (#11700)

* More robust guest members for users and tests for it

* Fixing shadow variables

* Fixing shadow variables

store/sqlstore/channel_store.go

@@ -1939,7 +1939,7 @@ func (s SqlChannelStore) AnalyticsDeletedTypeCount(teamId string, channelType st
 
 func (s SqlChannelStore) GetMembersForUser(teamId string, userId string) (*model.ChannelMembers, *model.AppError) {
 	var dbMembers channelMemberWithSchemeRolesList
-	_, err := s.GetReplica().Select(&dbMembers, CHANNEL_MEMBERS_WITH_SCHEME_SELECT_QUERY+"WHERE ChannelMembers.UserId = :UserId AND (Teams.Id = :TeamId OR Teams.Id IS NULL)", map[string]interface{}{"TeamId": teamId, "UserId": userId})
+	_, err := s.GetReplica().Select(&dbMembers, CHANNEL_MEMBERS_WITH_SCHEME_SELECT_QUERY+"WHERE ChannelMembers.UserId = :UserId AND (Teams.Id = :TeamId OR Teams.Id = '' OR Teams.Id IS NULL)", map[string]interface{}{"TeamId": teamId, "UserId": userId})
 	if err != nil {
 		return nil, model.NewAppError("SqlChannelStore.GetMembersForUser", "store.sql_channel.get_members.app_error", nil, "teamId="+teamId+", userId="+userId+", err="+err.Error(), http.StatusInternalServerError)
 	}