**Steps to replicate the issue** (include links if applicable):
* Easiest way to reproduce: Do an intitle search for a namespace name (such as `intitle:"Project"`), for example https://en.wikipedia.org/w/index.php?search=intitle%3A%22Wikipedia%22&title=Special%3ASearch&ns0=1
* Click on the "Redirect from" red links and note the page titles.
**What happens?**:
The namespace name is doubled. For example, upon clicking on the "Wikipedia:INTADMIN" redlink in the search results of the link above, we are met with the page title "Wikipedia:Wikipedia:INTADMIN".
Also, some redirects do not exist and have never existed, for example "Wikipedia:Wikipedia:REDIRECT" to "Minecraft". "Wikipedia:REDIRECT" does not redirect to "Minecraft" either.
**What should have happened instead?**:
The namespace name should not be doubled; we should never have been taken to "Wikipedia:Wikipedia:INTADMIN".
Additionally, the results should not listed on search results, since the nonexistent redirect pages don't exist, meaning the title doesn't match the condition.
**Software version** (on `Special:Version` page; skip for WMF-hosted wikis like Wikipedia): 1.43.0-wmf.17 (21482f8); I later was able to reproduce this on MediaWiki.org running 1.43.0-wmf.18 (38066e5).
**Other information** (browser name/version, screenshots, etc.):
{F57272323}
{F57272322}