[MusicXML import] corruption caused by whole-measure rests with type whole

MusicXML files with whole-measure rests which have type "whole" but a duration unequal to whole result in score corruption: the rest duration is incorrectly set to 1/1. On import a dialog with errors such as "Measure 1 Staff 1 incomplete. Expected: 1/4; Found: 1/1" is shown.

These rests are generated by Sibelius 7.1.3 Direct export.

Example score attached.