Sitecore GetItemUrl method is leaving off the http or https

I had a Lucene computed index field which was indexing item URLs on a multi site environment. The URLs being returned by LinkManager.GetItemUrl were coming back in an unexpected format: ://myUrl instead of http://myUrl. This was because the scheme element was missing off of the site definiton:

<site hostName="MySite" name="mysite" scheme="http" ... />

Aka the scheme element needs to be present otherwise the link manager will not include the protocol.