ve.Element: Fallback to body, window is not scrollable

Bug: 54928
Change-Id: Ifec0dae598f7fd99270588bd8ca77777a07e9669
(cherry picked from commit f6d409e09bb9513f1a1f5216e081aaa908a4277e)
Merge "ve.Element: Fallback to body, window is not scrollable" into wmf/1.22wmf20