Fix broken configs with non-existent components

[jesserockz]

What does this implement/fix?

Fixes a regression from #5139

ERROR Unexpected exception while reading configuration:
Traceback (most recent call last):
  File "/home/jesse/workspace/esphome/esphome/venv/bin/esphome", line 33, in <module>
    sys.exit(load_entry_point('esphome', 'console_scripts', 'esphome')())
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jesse/workspace/esphome/esphome/esphome/__main__.py", line 1041, in main
    return run_esphome(sys.argv)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/home/jesse/workspace/esphome/esphome/esphome/__main__.py", line 1019, in run_esphome
    config = read_config(dict(args.substitution) if args.substitution else {})
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jesse/workspace/esphome/esphome/esphome/config.py", line 1062, in read_config
    res = load_config(command_line_substitutions)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jesse/workspace/esphome/esphome/esphome/config.py", line 916, in load_config
    return _load_config(command_line_substitutions)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jesse/workspace/esphome/esphome/esphome/config.py", line 904, in _load_config
    result = validate_config(config, command_line_substitutions)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jesse/workspace/esphome/esphome/esphome/config.py", line 832, in validate_config
    result.run_validation_steps()
  File "/home/jesse/workspace/esphome/esphome/esphome/config.py", line 143, in run_validation_steps
    task.step.run(self)
  File "/home/jesse/workspace/esphome/esphome/esphome/config.py", line 318, in run
    if component.multi_conf_no_default and isinstance(self.conf, core.AutoLoad):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'multi_conf_no_default'

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other

Related issue or feature (if applicable): fixes

Pull request in esphome-docs with documentation (if applicable): esphome/esphome-docs#

Test Environment

• ESP32
• ESP32 IDF
• ESP8266
• RP2040
• BK72xx
• RTL87xx

Example entry for config.yaml:

# Example config.yaml

Checklist:

• The code change is tested and works locally.
• Tests have been added to verify that the new code works (under tests/ folder).

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in esphome-docs.