Fix a false positive for Rails/WhereMissing when left_joins(:foo)and where(foos: {id: nil}) separated by or, and

[ydah]

This PR is fix a false positive for Rails/WhereMissing when left_joins(:foo) and where(foos: {id: nil}) separated by or, and.

It is necessary to consider the following cases, which are separated by or or and.

Foo.left_joins(:foo).or(Foo.where(foos: {id: nil}))
Foo.where(foos: {id: nil}).and(Foo.left_joins(:foo))

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• Commit message starts with [Fix #issue-number] (if the related issue exists).
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• Squashed related commits together.
• Added tests.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.
• [-] If this is a new cop, consider making a corresponding update to the Rails Style Guide.

[ydah]

Thank you for your review. I updated this PR.

[koic]

Thanks!