Update mechanism is broken for SourceTree 1.2.3

I'm doing work in VMs for each client.

Every now and then, I need to do some work for a client for which work hasn't been done in a long while, so I:

• open the VM
• update it to the latests Windows patches and tools updates

In this case the VM has SourceTree 1.2.3 on it, which when checking for updates happily indicates

    [Checking for updates]
    Your software is up to date
    [OK]

In the background it downloads http://www.sourcetreeapp.com/update/windowsupdates.txt

so it looks the format of that file is now changed to something 1.2.3 cannot interpret any more.