Hovering "handsontable" cell type header handles won't throw an error

[wszymanski]

Context

The fix provided within PR #10458 has been reverted. I tried to fix the problems found after the release. However, after investigation, I suggested new changes. Probably it will fix also #10359.

It seems that mousedown event attached to HOT's root element is executed twice when we have HOT in HOT element. One event is called for the main instance and the second is for the editor being a Handsontable.

This PR adds an extra conditional, which checks whether a callback should be executed.

How has this been tested?

Tested on cases mentioned in the issues.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature or improvement (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Additional language file or change to the existing one (translations)

Related issue(s):

1. https://github.com/handsontable/dev-handsontable/issues/519
2. Hovering "handsontable" cell type header handles won't throw an error #10458
3. Hovering embedded table header cell crashes the app #10359

Affected project(s):

• handsontable
• @handsontable/angular
• @handsontable/react
• @handsontable/vue
• @handsontable/vue3

Checklist:

• I have reviewed the guidelines about Contributing to Handsontable and I confirm that my code follows the code style of this project.
• My change requires a change to the documentation.

[github-actions]

Launch the local version of documentation by running:

npm run docs:review ccf5398e9df83c6337e3b261597347f60f412099