Cannot call `nextSibling` of null

[hbrysiewicz]

Describe the bug:

While upgrading from Ember 3.7 to 3.8 I encountered an issue where any modal-dialog component I used with tetherTarget attribute would fire an issue deep in the internals of Ember/Glimmer runtime that said Cannot call nextSibling of null.

Work around:

It appears that the modal-dialog component has tagName: '' set by default. By setting tagName="div" on instantiation of the modal-dialog component I was able to avoid this error.

Cause:

I'm not 100% clear on the cause but it seems like the modal-dialog is being used as a node by the runtime but having no DOM element confuses it. This may be a runtime error, and not a modal-dialog bug, but starting issue here as this addon probably needs to be upgraded and will likely find the same issue.

[lukemelia]

@hbrysiewicz thanks for reporting this. I've reproduced it and have confirmed your workaround. I'm equally at a loss about what is going on.