Steps to replicate the issue (include links if applicable):

• Create an Upload Campaign with a homeButton link specified.
• Go through the upload process and then click on the link on the last page.

What happens?:

The link goes to https://commons.wikimedia.org/w/SPECIFIEDPAGE which does not exists and just shows an error page.

What should have happened instead?:

The link should go to https://commons.wikimedia.org/wiki/SPECIFIEDPAGE instead.

Software version (on Special:Version page; skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):
Notes for QA - will need to create a campaign with this config

{
	"enabled": true,
	"title": "Some title",
	"display": {
		"homeButton": {
			"label": "Some label",
			"target": "<target>"
		}
	}
}

... and test with target set to:

• the string 'useObjref'
• an absolute url
• a main-namespace page title
• a non-main-namespace page title