Add db migration to fix broken double puppets

database/upgrades/00-latest-revision.sql

@@ -1,4 +1,4 @@
--- v0 -> v9: Latest revision
+-- v0 -> v10: Latest revision
 
 CREATE TABLE guild (
     dcid       TEXT PRIMARY KEY,

database/upgrades/10-remove-broken-double-puppets.sql

@@ -0,0 +1,2 @@
+-- v10: Remove double puppet ghosts added while there was a bug in the bridge
+DELETE FROM puppet WHERE id='';