[Capella Import] corrupt file when importing capx file with pickup measure

Importing the attached capx file produces a corrupt MuseScore file:

Measure 1 Staff 1 incomplete. Expected: 4/4; Found: 4/8
Measure 1 Staff 2 incomplete. Expected: 4/4; Found: 2/4

That measure looks like a pickup measure:

But measure properties reveals that is is not. Changing measure properties 'actual diration' to 2/4 causes a crash in MuseScore 2.0.2. In the current nightly builds there is no crash, but an entirely empty measure instead.

Reported in https://musescore.org/de/node/81361