Do not block UI when this page didn't have slice

This CL before, if controller have UIBlocker interface
will going to blocker condition to make whole page
invisible for a certain time until slice is fully loaded.

This CL add the check condition that if the controller
have UIBlocker inferface but didn't have slice uri will
not go to blocker condition.

Bug: 141292712
Test: make -j42 RunSettingsRoboTests ROBOTEST_FILTER=DashboardFragmentTest
Change-Id: I79daae131654f8fd823a9c8f1be46ad6c7921908