Gallery with no images (invalid characters as gallery contents) creates an invisible node and can't be edited.
For example, create a page with the following wikitext:
<gallery> >> </gallery>
Example: https://en.wikipedia.org/w/index.php?title=User:Matma_Rex/sandbox&oldid=826934821
This renders as an empty gallery (<ul class="gallery mw-gallery-traditional"></ul>).
In VE, it displays a placeholder, but it seems that it can't be clicked to focus it:
When focussed using arrow keys, it displays a completely mispositioned context menu:
Trying to use the "Edit" button causes a JS error in the console:
TypeError: Cannot read property 'toggleHighlighted' of undefined
at VeUiMWGalleryDialog.ve.ui.MWGalleryDialog.onHighlightItem (https://en.wikipedia.org/w/extensions/VisualEditor/modules/ve-mw/ui/dialogs/ve.ui.MWGalleryDialog.js?22058:591:7)
at https://en.wikipedia.org/w/extensions/VisualEditor/modules/ve-mw/ui/dialogs/ve.ui.MWGalleryDialog.js?22058:342:13
at fire (https://en.wikipedia.org/w/load.php?debug=true&lang=en&modules=jquery%2Cmediawiki%7Cmediawiki.legacy.wikibits&only=scripts&skin=vector&version=14kbqyi:3317:31)
at Object.add [as done] (https://en.wikipedia.org/w/load.php?debug=true&lang=en&modules=jquery%2Cmediawiki%7Cmediawiki.legacy.wikibits&only=scripts&skin=vector&version=14kbqyi:3376:7)
at VeUiMWGalleryDialog.<anonymous> (https://en.wikipedia.org/w/extensions/VisualEditor/modules/ve-mw/ui/dialogs/ve.ui.MWGalleryDialog.js?22058:341:9)
at https://en.wikipedia.org/w/resources/lib/oojs-ui/oojs-ui-windows.js?f9a29:748:28
at mightThrow (https://en.wikipedia.org/w/load.php?debug=true&lang=en&modules=jquery%2Cmediawiki%7Cmediawiki.legacy.wikibits&only=scripts&skin=vector&version=14kbqyi:3583:29)
at process (https://en.wikipedia.org/w/load.php?debug=true&lang=en&modules=jquery%2Cmediawiki%7Cmediawiki.legacy.wikibits&only=scripts&skin=vector&version=14kbqyi:3651:12)