Fix IntlExtension::formatDateTime use of date formatter prototype

[drjayvee]

See twigphp/intl-extra#6 for more details

[stof]

It would be great to have tests to prevent regressions.

[drjayvee]

It would be great to have tests to prevent regressions.

Voilà!

[fabpot]

Thank you @drjayvee.

[fabpot]

Merged

[keulinho]

This change seems to break the fallback of using the timezone set in twigs CoreExtension.
The issue seems to be in this line:

        if (false === $formatterTimezone) {
            $formatterTimezone = $date->getTimezone();

$formatterTimezone is basically never false, as if it is not provided directly it is null, so the timezone from the converted date (which is based on the one configured in the CoreExtension) is never used.

Quickfix would be to use:

        if (null === $formatterTimezone) {
            $formatterTimezone = $date->getTimezone();