Show container controls, when inline record is deleted
The following problem is present since TYPO3, when jsfunc.inline.js was rebuilt to InlineControlContainer.js.
In the inline control container, the buttons "Add media", "Select & upload files", ..., are automatically hidden when the maxitems limit has been reached.
The buttons are supposed to be shown again, once the user removes a record in the backend form. This however is now broken in the function "toggleContainerControls" in InlineControlContainer.js, because the code only handles "a" tags, while the inline control buttons are "button" tags.