Fix tree closer.  Deal with none case for PFQ.
Fix tree closer.  Deal with none case for PFQ.

Change-Id: Ia7883c196c688236051a4637561c9a01be5358cb

BUG=TreeCloser
TEST=Ran with simple prefix for x86-generic and no keys

Review URL: http://codereview.chromium.org/6480085

sigma/coreos-scripts,coreos/scripts,marineam/coreos-scripts,gtank/scripts,bcwaldon/coreos-scripts,mischief/scripts,BugRoger/scripts,marineam/coreos-scripts,sigma/coreos-scripts,mjg59/scripts,mjg59/scripts,smilart/scripts,glevand/coreos--scripts,zhang0137/scripts,crawford/scripts,zhang0137/scripts,nicescale/scripts,smilart/scripts,vmware/coreos-scripts,fivethreeo/scripts,trnubo/scripts,vmware/coreos-scripts,zhang0137/scripts,endocode/scripts,trnubo/scripts,mjg59/scripts,andrejro/coreos--scripts,bcwaldon/coreos-scripts,vmware/coreos-scripts,andrejro/coreos--scripts,BugRoger/scripts,marineam/coreos-scripts,smilart/scripts,crawford/scripts,coreos/scripts,bcwaldon/coreos-scripts,glevand/coreos--scripts,endocode/scripts,andrejro/coreos--scripts,sigma/coreos-scripts,fivethreeo/scripts,BugRoger/scripts,trnubo/scripts,gtank/scripts,mischief/scripts,crawford/scripts,endocode/scripts,mischief/scripts,nicescale/scripts,gtank/scripts,nicescale/scripts,fivethreeo/scripts