Empty "errors" check

[bartzantingh]

Add type assertion and check for empty "errors" array returned from rule to prevent crashes when converting to []interface{}

Issue #107

[github-actions]

Merging this branch will decrease overall coverage

Impacted Packages	Coverage Δ	🤖
github.com/mxlint/mxlint-cli/lint	75.38% (-0.06%)	👎

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Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/mxlint/mxlint-cli/lint/lint_rego.go	89.89% (-0.92%)	89 (+2)	80 (+1)	9 (+1)	👎

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.