First reported here: https://github.com/wikimedia/wikipedia-preview/issues/182
Although that report is light in details, I experienced this issue during recent development.
If the popupContainer init parameter is provided but invalid, the code fails with a low-level error.
We should validate it and fallback to the default value instead of erroring out.
QA Results - Diff Local
| AC | Status | Details |
|---|---|---|
| 1 | ✅ | T361703#9861934 |