While researching issue #1551, I came across some minor problems.
When a spreadsheet does not have a title, which is often the case for spreadsheets created with Excel (note that this is not the case for spreadsheets created with PhpSpreadsheet), if you try to save it as Html, it throws an exception. It will now use the sheet title of the active sheet as a title in this case.
When writing an Html spreadsheet using `useInlineCss(true)`, gridlines are not handled properly. This is addressed by adding `class=gridlines gridlinesp` to the cell's `td` tag, and by suppressing any border attributes which would be styled as `none #000000`. It would be unusual to turn off gridlines for specific cells, but that can still be accomplished by using `Border::BORDER_NONE` in conjunction with any color other than `#000000` - see new test `testHideSomeGridlines`.
While we might never be able to have 100% of our code strict, we can at
the very least do it for all of our tests. This ensures that our tests
are using our API with the types as intended by the test author, and not
silently be cast to what our API requires.
* Html Writer Styles when Using Inline Css
Fix#3678. Problem introduced by PR #3016. Combining `td` and `th` styles into a single declaration greatly reduces file size when `useInlineCss` is false, which is the default. However, generating code with the non-default option was not changed to use the combined declaration, so styling was lost. This PR rectifies that error.
* Apostrophe Rather Than Quote
oleibman
Adrien Crivelli