Initialize a present fence in case of failure

Speculative fix for b/304586546. By inspection, we've found this is a
case where SF does not initialize a present fence. If HWC does not
replace it with a real one, this could lead to a crash later.

Bug: 304586546
Test: make
Change-Id: I770f2feb21721de30d0e8f099a365665f81bf0d3