Eat AttributeError in peewee close database call

Fixes https://sentry.io/coreos/backend-production/issues/104257892/

data/database.py

@@ -305,6 +305,7 @@ get_epoch_timestamp_ms = lambda: int(time.time() * 1000)
 
 
 def close_db_filter(_):
+  try:
     if not db.is_closed():
       logger.debug('Disconnecting from database.')
       db.close()
@@ -312,6 +313,10 @@ def close_db_filter(_):
     if read_slave.obj is not None and not read_slave.is_closed():
       logger.debug('Disconnecting from read slave.')
       read_slave.close()
+  except AttributeError:
+    # If the database is closed between the time we check on line 309 and db.close() is called on
+    # 311, then an AttributeError will be raised. Simply eat this exception and continue onward.
+    pass
 
 
 class QuayUserField(ForeignKeyField):