Make sure to properly set NULL for portal.mxid if we don't have one.

When this gets set to empty string it causes primary key to fail and cascades
into other issues like the inability to deduplicate messages.

Refs #26

database/portal.go

@@ -51,13 +51,21 @@ func (p *Portal) Scan(row Scannable) *Portal {
 	return p
 }
 
+func (p *Portal) mxidPtr() *id.RoomID {
+	if p.MXID != "" {
+		return &p.MXID
+	}
+
+	return nil
+}
+
 func (p *Portal) Insert() {
 	query := "INSERT INTO portal" +
 		" (channel_id, receiver, mxid, name, topic, avatar, avatar_url," +
 		" type, dmuser, first_event_id)" +
 		" VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)"
 
-	_, err := p.db.Exec(query, p.Key.ChannelID, p.Key.Receiver, p.MXID,
+	_, err := p.db.Exec(query, p.Key.ChannelID, p.Key.Receiver, p.mxidPtr(),
 		p.Name, p.Topic, p.Avatar, p.AvatarURL.String(), p.Type, p.DMUser,
 		p.FirstEventID.String())
 
@@ -72,7 +80,7 @@ func (p *Portal) Update() {
 		" dmuser=$7, first_event_id=$8" +
 		" WHERE channel_id=$9 AND receiver=$10"
 
-	_, err := p.db.Exec(query, p.MXID, p.Name, p.Topic, p.Avatar,
+	_, err := p.db.Exec(query, p.mxidPtr(), p.Name, p.Topic, p.Avatar,
 		p.AvatarURL.String(), p.Type, p.DMUser, p.FirstEventID.String(),
 		p.Key.ChannelID, p.Key.Receiver)