v1.25.2: Fixed DateTime::getLastErrors() returning false on PHP 8.2+

[MarkCay]

Before PHP 8.2.0, DateTime::getLastErrors() did not return false when there were no warnings or errors. Instead, it would always return the documented array structure. (https://www.php.net/manual/en/datetimeimmutable.getlasterrors.php#refsect1-datetimeimmutable.getlasterrors-changelog)

This patch ensures that the array_sum() will not receive a false as a parameter.

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[MarkCay]

Hi @rappasoft @lrljoe, just to clarify — do I need to complete all 9 tasks before this PR can be reviewed? I left the last four unchecked since my changes aren’t related to New Feature Submissions. Thanks! ☺️