[11.x] Handle Null Check in Str::startsWith and Str::endsWith

[onairmarc]

This PR adds a null check to the $haystack parameter. Null values for this parameter have been deprecated, causing error messages to be logged. If $haystack is null, then Str::startsWith and Str::endsWith will return false.

[shaedrich]

Wouldn't it be better to either throw an exception or target master and enforce the argument types in the method signature instead of the PHPDoc?

[onairmarc]

Wouldn't it be better to either throw an exception or target master and enforce the argument types in the method signature instead of the PHPDoc?

The PHPDoc didn't come from me. I forgot to turn off auto-formatting in my IDE, so those changes are me reverting what my IDE did automatically. I think early returning false is still appropriate, considering the haystack is null, so the haystack string implicitly does not start or end with the needle string.

[vlakoff]

Related past PRs, for handling $needles being an array containing a null value: #30364 and #37087.

[vlakoff]

For consistency, this handling of null haystack should be made to contains() as well.

Note: when using the "ignoreCase" mode, make sure that mb_strtolower() doesn't receive the null haystack (return before).