Widen bools before storing them

Summary: The testcase stored an unwidened bool with garbage in
the high 56 bits prior to this fix (and asserted in dbg builds).

Reviewed By: @alexmalyshev

Differential Revision: D1648569

Signature: t1:1648569:1414630806:9622d3981838ad3cf92cc055905f6057e7e9f8cf