Handle duplicate logins (ref #408)

database/upgrades/16-refactor-postgres.sql

@@ -50,7 +50,7 @@ ALTER TABLE portal ADD CONSTRAINT portal_mxid_unique UNIQUE(mxid);
 -- Delete any portals that aren't associated with logged-in users.
 DELETE FROM portal WHERE receiver<>'' AND receiver NOT IN (SELECT username FROM "user" WHERE uuid IS NOT NULL);
 -- Change receiver to uuid instead of phone number, also add nil uuid for groups.
-UPDATE portal SET receiver=(SELECT uuid FROM "user" WHERE username=receiver) WHERE receiver<>'';
+UPDATE portal SET receiver=(SELECT uuid FROM "user" WHERE username=receiver LIMIT 1) WHERE receiver<>'';
 UPDATE portal SET receiver='00000000-0000-0000-0000-000000000000' WHERE receiver='';
 -- Drop the foreign keys again to allow changing types (the ON UPDATE CASCADEs are needed for the above step)
 ALTER TABLE message DROP CONSTRAINT message_portal_fkey;

database/upgrades/17-refactor-sqlite.sql

@@ -91,7 +91,7 @@ CREATE TABLE lost_portals (
 );
 INSERT INTO lost_portals SELECT mxid, chat_id, receiver FROM portal WHERE mxid<>'';
 DELETE FROM portal WHERE receiver<>'' AND receiver NOT IN (SELECT username FROM "user" WHERE uuid<>'');
-UPDATE portal SET receiver=(SELECT uuid FROM "user" WHERE username=receiver) WHERE receiver<>'';
+UPDATE portal SET receiver=(SELECT uuid FROM "user" WHERE username=receiver LIMIT 1) WHERE receiver<>'';
 UPDATE portal SET receiver='00000000-0000-0000-0000-000000000000' WHERE receiver='';
 DELETE FROM portal WHERE chat_id NOT LIKE '________-____-____-____-____________' AND LENGTH(chat_id) <> 44;
 DELETE FROM lost_portals WHERE mxid IN (SELECT mxid FROM portal WHERE mxid<>'');