fix(rules): handle blank commit message in signed-off-by rule

[SetDefaultOne]

Check for an empty commit message for rule signed-off-by.

Description

On a minimal environment with only commitlint installed and the signed-off-by rule set, writing an empty commit message would result in a runtime exception.

Motivation and Context

Previously this rule caused a runtime exception trying to validate an empty commit message as it was trying to access the startsWith string method on an undefined value which was supposed to store the last line of the commit message. Now it does a check to see if the last line is undefined or not.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have added tests to cover my changes.
• All new and existing tests passed.

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[escapedcat]

Thanks!

[escapedcat]

Had some issues during the publish but version 19.4.1 should work for you. Give it a try.

[SetDefaultOne]

Had some issues during the publish but version 19.4.1 should work for you. Give it a try.

Thanks. I've already set up v19.4.1 and it's working as intended.