[5.1] Fix for legacy editor-xtd plugins with array of buttons

[Fedik]

Pull Request for Issue #43128 .

Summary of Changes

Fix compatibility with legacy editor-xtd plugins, which return multiple buttons.

Testing Instructions

Edit

joomla-cms/plugins/editors-xtd/contact/src/Extension/Contact.php

Line 46 in ef33d44

public function onDisplay($name)

And replace whole method with:

public function onDisplay($name)
{
  return [
    new CMSObject([
        'action'  => 'insert',
        'icon'    => 'foobar',
        'text'    => 'Beer',
        'options' => ['content' => '🍺 ']
    ]),
    new CMSObject([
        'action'  => 'insert',
        'icon'    => 'foobar',
        'text'    => 'Cat',
        'options' => ['content' => '🐈 ']
    ]),
  ];
}

Go to content editing. And check for this button.

Actual result BEFORE applying this Pull Request

Only Cat button is shown.

Expected result AFTER applying this Pull Request

Both buttons is shown.

Link to documentations

Please select:

• Documentation link for docs.joomla.org:
• No documentation changes for docs.joomla.org needed
• Pull Request link for manual.joomla.org:
• No documentation changes for manual.joomla.org needed

[Tazzios]

I have tested this item ✅ successfully on 07ebef5

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/43129.}

[viocassel]

I have tested this item ✅ successfully on 07ebef5

---

_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/43129.}

[Quy]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/43129.}

[HLeithner]

This pull request has been automatically rebased to 5.1-dev.

[LadySolveig]

Thank you @Fedik and for testing @Tazzios and @viocassel