Description:
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When trying to add the empty directory '/' to a phar archive PHP throws a fatal error:
PHP Fatal error:  Possible integer overflow in memory allocation (1 * 18446744073709551615 + 1) in /path/to/my/script.php on line 91

The same action works in ZipArchive, i.e. this works:
$zip = new \ZipArchive;
$zip->open(tempnam(sys_get_temp_dir(), "phptest"));
$zip->addEmptyDir("/");

Test script:
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$tar = new \PharData("/tmp/phptempfile");
$tar->addEmptyDir("/");
// Fatal error Possible Integer overflow