Show loading view in installer component properly

[magnussinger]

Pull Request for Issue #37516

Note: this PR is the rebase to 4.1-dev for this PR: #37538 (had to create a new one because I messed something up on the other one)

Summary of Changes

When removing the "hidden" class from the loading view in the installer component in the inspector, this view is now properly positioned

Testing Instructions

Go to the extension installer, open the inspector and search for the div with the ID "loading", then remove the "hidden" class from it

Actual result BEFORE applying this Pull Request

The loading view was positioned below the main content and was invisible

Expected result AFTER applying this Pull Request

The loading view is now visible and properly positioned

Documentation Changes Required

None

[richard67]

I have tested this item ✅ successfully on 01bed1d

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/37570.}

[richard67]

@brianteeman Could you test this PR, too? It's the same as #37538 , but this time for the 4.1-dev branch. Thanks in advance.

[brianteeman]

I have tested this item ✅ successfully on 01bed1d

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/37570.}

[richard67]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/37570.}

[laoneo]

Thanks!!