[BUG] error KeyError: 'master_list' in sali-minion 3005.1 logs

Description
Soon after minion process is started there is an error in the logs

2023-07-08 12:05:08,966 [salt.minion      :232 ][DEBUG   ][19917] Master URI: tcp://127.0.0.1:4506
2023-07-08 12:05:08,975 [salt.utils.event :315 ][DEBUG   ][19917] SaltEvent PUB socket URI: /var/run/salt/minion/minion_event_e6adef2bc4_pub.ipc
2023-07-08 12:05:08,975 [salt.utils.event :316 ][DEBUG   ][19917] SaltEvent PULL socket URI: /var/run/salt/minion/minion_event_e6adef2bc4_pull.ipc
2023-07-08 12:05:08,976 [salt.utils.event :821 ][DEBUG   ][19917] Sending event: tag = __master_failback; data = {'master': '127.0.0.1', '_stamp': '2023-07-08T12:05:08.976638'}
2023-07-08 12:05:08,977 [salt.transport.ipc:373 ][DEBUG   ][19917] Closing IPCMessageClient instance
2023-07-08 12:05:08,978 [salt.channel.client:313 ][DEBUG   ][19917] Closing AsyncReqChannel instance
2023-07-08 12:05:08,978 [salt.minion      :2690][DEBUG   ][19693] Minion of 'salt-a.domain.' is handling event tag '__master_failback'
2023-07-08 12:05:08,980 [tornado.application:356 ][ERROR   ][19693] Future <salt.ext.tornado.concurrent.Future object at 0x7f2e94f49588> exception was never retrieved: Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/salt/ext/tornado/gen.py", line 309, in wrapper
    yielded = next(result)
  File "/usr/lib/python3/dist-packages/salt/minion.py", line 2748, in handle_event
    if data["master"] != self.opts["master_list"][0]:
KeyError: 'master_list'
2023-07-08 12:05:08,980 [salt.minion      :2690][DEBUG   ][19693] Minion of 'salt-b.domain.' is handling event tag '__master_failback'
2023-07-08 12:05:08,980 [tornado.application:356 ][ERROR   ][19693] Future <salt.ext.tornado.concurrent.Future object at 0x7f2e94f49588> exception was never retrieved: Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/salt/ext/tornado/gen.py", line 309, in wrapper
    yielded = next(result)
  File "/usr/lib/python3/dist-packages/salt/minion.py", line 2748, in handle_event
    if data["master"] != self.opts["master_list"][0]:
KeyError: 'master_list'

Setup
salt-minion config

master:
  - salt-a.domain
  - salt-b.domain.
master_type: str
renderer: yaml_jinja
log_level_logfile: debug
log_level: info

Steps to Reproduce the behavior
Restart salt minion process

Expected behavior
No errors in the log

Versions Report

salt-minion --versions-report
Salt Version:
          Salt: 3005.1

Dependency Versions:
          cffi: Not Installed
      cherrypy: Not Installed
      dateutil: 2.6.1
     docker-py: Not Installed
         gitdb: 2.0.3
     gitpython: 2.1.8
        Jinja2: 2.10
       libgit2: 0.26.0
      M2Crypto: Not Installed
          Mako: Not Installed
       msgpack: 0.5.6
  msgpack-pure: Not Installed
  mysql-python: Not Installed
     pycparser: Not Installed
      pycrypto: 2.6.1
  pycryptodome: 3.4.7
        pygit2: 0.26.2
        Python: 3.6.9 (default, Oct  8 2020, 12:12:24)
  python-gnupg: 0.4.1
        PyYAML: 3.12
         PyZMQ: 17.1.2
         smmap: 2.0.3
       timelib: Not Installed
       Tornado: 4.5.3
           ZMQ: 4.2.5

System Versions:
          dist: ubuntu 18.04 Bionic Beaver
        locale: UTF-8
       machine: x86_64
       release: 5.4.0-1035-aws
        system: Linux
       version: Ubuntu 18.04 Bionic Beaver

Start in salt/minion.py at handle_event around line 2748, where the __master_failback event accesses master_list. Reproduce by restarting a minion with the multi-master configuration shown, then verify that the restart produces no KeyError or related error in the logs.