mw.ViewPageTarget: Check elementsThatHadOurAccessKey before accessing

Follows-up I31d6b9ea065b3be85ed0.

Bug: 62329
Change-Id: I83a6f20cafd6193d64142914f72c1496d03294a5
(cherry picked from commit 8735ea2ef9bcd1325ead46ad83197ae3b3469e3c)