In MediaWiki 1.35 with CreatePage version ee8d707, when a user clicks on 'Create page' without filling a page title, an exception is thrown in SpecialCreatePageRedirect::execute.
{
"class": "TypeError",
"message": "Argument 1 passed to SpecialCreatePageRedirect::getTargetURL() must be an instance of Title, null given, called in /mediawiki/extensions/CreatePage/SpecialCreatePageRedirect.php on line 44",
"code": 0,
"file": "/mediawiki/extensions/CreatePage/SpecialCreatePageRedirect.php:51",
"trace": [
"/mediawiki/extensions/CreatePage/SpecialCreatePageRedirect.php:44",
"/mediawiki/includes/specialpage/SpecialPage.php:600",
"/mediawiki/includes/specialpage/SpecialPageFactory.php:635",
"/mediawiki/includes/MediaWiki.php:307",
"/mediawiki/includes/MediaWiki.php:940",
"/mediawiki/includes/MediaWiki.php:543",
"/mediawiki/index.php:53",
"/mediawiki/index.php:46"
]
}It should be checked if the title is null and return an explicit error in this case (with a user message to be created).
Also it would be nice to also warn the user when they clicks on 'Create page' with some JavaScript, possibly with the same user message.