Pop-up doesn’t work if Classic block editor is itself a pop-up

As of WordPress 6.3, this plugin does not work anymore in the blocks editor if the Classic block is rendered as a modal. The reason is that the pop-up form has become inaccessible due to a modal being in the way.

Expected behaviour:

* Start a new page or blog post.
* Select the Classic block.
* An inline editor appears.
* Click the “By” button.
* Fill out the image credits form.
* Press “Submit” to inject the formatted contents of the form into the block.

Actual behaviour:

* Start a new page or blog post.
* Select the Classic block.
* A modal editor appears.
* Click the “By” button.
* The plug-in’s modal is rendered behind the Classic block’s modal. The only way you can use the former is by closing the latter, at which point you can no longer insert the content generated by the former into the (closed) latter.

The change of the Classic block was unannounced (at least not in the WordPress 6.3 announcement) and is currently full of bugs, some of which simply stem from the choice of having the classic block editor being a modal in the first place, e.g. you cannot edit the block settings; if you want to edit the text afterwards, you need to click a button first.

Initially I thought all Classic block editors had been changed to modals until I saw on another site I manage and that I had also upgraded to 6.3 that there the Classic block editor was still rendered inline.

I am not sure what causes the Classic block editor to be rendered inline or as a modal, maybe some plugin or theme is running interference.

The easiest way for me as the plugin’s author to deal with this problem would be to wait until the WordPress developers have fixed the most important problems with this block, but that could take a while.

Therefore I plan on creating a workaround in the short to medium turn. I do not know when yet. If you are a user of this plug-in and are bothered by this bug, please let me know in the comments. This helps me determine how urgent the fixing of this bug is.

My apologies if this report has odd formatting: the Support forums have started using Gutenberg blocks.