Just discovered this with the demo bug tracker. When visiting the bug tracker while not already logged in, the code detects that the anonymous user has access to a single project. It then attempts to set this on the user preference as the default project. This has two issues:

• It attempts to change preferences of a protected user, hence, causing an error.
• It generates SQL updates even if the preference is already set, hence extra load.

We should fix both.

I'm not 100% sure this repros on 1.2.11, but it didn't in the demo instance and the latest code for master-1.2.x which we are basing 1.2.12 on.