Steps to reproduce the issue

1. Set default editor to Editor - None or Editor - CodeMirror
2. Create a custom module
3. In the .xml file, create two separate <fieldset> with a <field type="editor" /> each
4. Open the module in the backend to edit, swap to the second tab and try to open any editor extensions (ie. Media)

Expected result

The modal dialog appears

Actual result

The modal backdrop appears, but the modal dialog does not.

Additional comments

When inspecting the DOM elements, the issue appears to be that the modal dialog elements are placed in the first tab, and since tabs have a display:none when inactive, the dialog itself is also hidden.

I tested with TinyMCE, something about how that one is setup/instantiated has it either fix itself or just handle the modal dialogs differently.