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

• Edit a page and put {{PAGESIZE:mw:User:Test}} on the page and save (this requires the mw: prefix as interwiki in the interwiki table)
• Maybe run the job queue to update the links table

What happens?:
Look at the table linktarget, a row with lt_namespace = 0 and lt_Title = 'User:Test' is stored, but external links (like interwiki links) should not be stored in the templatelinks table.

What should have happened instead?:
No row in the templatelinks and linktarget table

Software version (skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):