Don't add falsy items to list (merge_packages)

[kellerza]

Description:

merge_pakages added falsy items to list (i.e. empty OrderedDict() from load_yaml added to automation list)

Related issue (if applicable): fixes #13412

FIXED Example entry for configuration.yaml (if applicable):

homeassistant:
  packages:
    empty_auto:
      automation: !include empty.yaml

automation:
  - alias: "Some valid automation"

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass

If the code does not interact with devices:

• Tests have been added to verify that the new code works.