Set outlier weight 1 when target is 0

[AntonZogk]

Add another condition for defaults
Add test case in test data
Fix commit hook noqa: E712

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Checklists

This pull request meets the following requirements:

• installable with all dependencies recorded
• runs without error
• follows PEP8 and project specific conventions
• appropriate use of comments, for example no descriptive comments
• functions documented using Numpy style docstings
• assumptions and decisions log considered and updated if appropriate
• unit tests have been updated to cover essential functionality for a reasonable range of inputs and conditions
• other forms of testing such as end-to-end and user-interface testing have been considered and updated as required
• tests suite passes (locally as a minimum)
• peer reviewed with review recorded

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[giuliag92]

Hi Anton, this looks great! Thank you for fixing E712. :)