Steps to Reproduce:
Configure a MediaWiki 1.35 instance with :
$wgNamespacesWithSubpages[NS_MAIN] = true;
Create and then attempt to edit a subpage with VisualEditor
Actual Results:
Error message: "Error contacting the Parsoid/RESTBase server: http-bad-status"
Expected Results:
VisualEditor loads without error.
Notes:
Only subpages are broken. VisualEditor seems to work well on normal pages. Also, editing source with VisualEditor works fine on all articles, even subpages.