Fix Notice on Joomla update with PHP 7.4

[degobbis]

Pull Request for Issue # .

Summary of Changes

A PHP Notice will be shown on Joomla Update with PHP 7.4.
This Patch solves this notice.

Testing Instructions

Needs Joomla 3.9.13 and PHP 7.4 installed
Go to Joomla administration -> Components -> Joomla! Update and -> Check for Updates

Expected result

An Update or the actual version for reinstallation will bi shown, without any PHP notices

Actual result

PHP Notice will shown

[brianteeman]

I have tested this item ✅ successfully on a4dd3cd

Replicated the issue and confirm the test does what it says

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/27219.}

[degobbis]

@brianteeman thx for testing

[viocassel]

I have tested this item ✅ successfully on a4dd3cd

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/27219.}

[Quy]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/27219.}

[degobbis]

@viocassel thx for testing

[zero-24]

Merging thanks for fixing this issue 👍