Subrooms: Fix more crashes (#4251)
Subrooms: Fix more crashes (#4251)

- Don't allow setting a room to be a subroom of itself.
- Don't allow setting a parent room to be a subroom
svivian/Pokemon-Showdown,sirDonovan/Pokemon-Showdown,Enigami/Pokemon-Showdown,svivian/Pokemon-Showdown,Zarel/Pokemon-Showdown,urkerab/Pokemon-Showdown,panpawn/Gold-Server,Enigami/Pokemon-Showdown,Enigami/Pokemon-Showdown,Zarel/Pokemon-Showdown,urkerab/Pokemon-Showdown,AustinXII/Pokemon-Showdown,AustinXII/Pokemon-Showdown,QuiteQuiet/Pokemon-Showdown,xfix/Pokemon-Showdown,svivian/Pokemon-Showdown,jumbowhales/Pokemon-Showdown,sirDonovan/Pokemon-Showdown,Zarel/Pokemon-Showdown,AustinXII/Pokemon-Showdown,svivian/Pokemon-Showdown,sirDonovan/Pokemon-Showdown,panpawn/Gold-Server,panpawn/Gold-Server,xfix/Pokemon-Showdown,panpawn/Pokemon-Showdown,xfix/Pokemon-Showdown,xfix/Pokemon-Showdown,jumbowhales/Pokemon-Showdown,QuiteQuiet/Pokemon-Showdown,xfix/Pokemon-Showdown,jumbowhales/Pokemon-Showdown,urkerab/Pokemon-Showdown,QuiteQuiet/Pokemon-Showdown,svivian/Pokemon-Showdown,panpawn/Pokemon-Showdown,Enigami/Pokemon-Showdown