Evaluating currentValue of a Loc that isn't the current Loc causes NPE

[farmdawgnation]

Attempting to evaluate currentValue on a Loc that's not the current Loc for the request appears to cause a NPE. I believe it's because the siteMap value for the Loc won't be set and we'll attempt to evaluate the globalParams for it here.

This should be as simple as wrapping that in some sort of nullary guard before evaluating. Or perhaps, installing a guard higher up that prevents any kind of evaluation of currentValue if the Loc isn't currently in use.