Please login or register displayed when registrations are turned off

My site has user registrations turned off, but signup still shows 'Please login or register to sign up'. The register link takes the user to an access denied page. Here's a simple patch that checks to make sure user registrations are allowed before showing the register link.

Note that there is a string comparison to 0 in the code, which with php can cause some unwanted effects (ie, "" == 0 returns TRUE). However since the variable is using a radio interface with the form API, I don't think its possible for it to have any other values other than 0, 1, or 2.