**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