ReferenceHelper@insertNewBefore checks for missing coordinates before replacing values

[orkhanahmadov]

This is:

- [x] a bugfix
- [ ] a new feature

Checklist:

• Changes are covered by unit tests
• Code style is respected
• Commit message explains why the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change
• Documentation is updated as necessary - not necessary

Why this change is needed?

Relates to this issue. When deleting a column before the last column with the null value it incorrectly keeps deleted columns value instead of copying the null/empty value from the last column. This PR fixes this issue by checking for missing coordinates and merging them with $allCoordiantes in insertNewBefore().

[oleibman]

For completeness, can you change your test to assert all the values in A1-C2 after removeCol rather than just B2?.

[orkhanahmadov]

For completeness, can you change your test to assert all the values in A1-C2 after removeCol rather than just B2?.

Good point. I made changes to PR, added assertions for cells in the test case. I also switched to array value checking instead of using getCell(), discovered that getCell() creates the cell if it is not available in the worksheet. If I used getCell() in a test case that solved the bug on its own, without any actual code changes. I modified my implementation to use createNewCell on the worksheet to create missing cells, but this required changing the visibility of the method from private to public

[oleibman]

Thank you for your contribution.