[4.0] House cleaning => remove obsolete div element in system message container

[hans2103]

Pull Request for Issue # .

Summary of Changes

This PR will remove the obsolete <div id="system-message"></div> from layout/joomla/system/message.php
This id was used in J3 plugin installer_webinstaller. It is not used in the J4 version anymore.
Therefor this element is obsolete and can be removed.
This PR will also remove the obsolete styling for this removed element.

Testing Instructions

• Joomla 4
• Find the login module in the sidebar, don't fill any fields and press the button login.
• The page refreshes on /index.php/author-login with an alert

Empty password not allowed.

The HTML of this alert is:

<div id="system-message-container" aria-live="polite"><joomla-alert type="warning" dismiss="true" class="joomla-alert--show" role="alert"><button class="joomla-alert--close" aria-label="Close"><span aria-hidden="true">×</span></button><div class="alert-heading"><span class="warning"></span><span class="sr-only">Warning</span></div><div class="alert-wrapper"><div class="alert-message">Empty password not allowed.</div></div></joomla-alert></div>

Press the X to close the alert

Actual result BEFORE applying this Pull Request

You are able to close the alert.
The HTML of the closed alert is:

<div id="system-message-container" aria-live="polite"><div id="system-message"></div></div>

Expected result AFTER applying this Pull Request

You are able to close the alert.
The HTML of the closed alert is:

<div id="system-message-container" aria-live="polite"></div>

Without the obsolete div element you can properly use the css :empty trigger to remove a margin between succeeding elements. No JS needed.

Documentation Changes Required

[infograf768]

I have tested this item ✅ successfully on 891ac39

OK for this.

@chmst #system-message-container needs to be added to Cassiopea css with margin-top: 0;

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/31195.}

[hans2103]

@chmst #system-message-container needs to be added to Cassiopea css with margin-top: 0;

No... only #system-message-container:empty and the :first-child of the parent of #system-message-container needs a margin-top:0.
This should be done after merge of this PR

[hans2103]

PR joomla/cassiopeia#194 is created to fix obsolete margin in Cassiopeia

[adj9]

I have tested this item ✅ successfully on 891ac39

OK

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/31195.}

[richard67]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/31195.}

[chmst]

Thanks!