[plg_quickicon_phpversioncheck] Avoid errors when Joomla! gets outdated

[SharkyKZ]

Pull Request for Issue #27195.

Summary of Changes

Fixes error that occurs when PHP version is unsupported and outdated Joomla! version doesn't know a recommended PHP version.

Testing Instructions

See #27195 (comment).

Expected result

No errors.

Actual result

Call to a member function format() on null

Documentation Changes Required

No.

[ReLater]

I have tested this item ✅ successfully on f99404e

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[alikon]

I have tested this item ✅ successfully on f524109

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[alikon]

RTC
previous test is still good

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[HLeithner]

Thanks for the better php EOL support sharky