loviewer says a document is corrupt when it's only protected by a password

Steps to reproduce:
1) Launch DocViewer
2) Pick from the list a LibreOffice document protected by a password
3) Try to load it with our LibreOfficeKit viewer.

What happens:
DocViewer will show a dialog, saying that the document is corrupt.

What should happens:
DocViewer's error message should consider that the document may be protected.

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LibreOfficeKit doesn't seem to be able to detect that a document is protected. The string lok::Office::getError() returns don't mention this possibility (just says that lok::Document is null).

For now, we can only update the error string at http://bazaar.launchpad.net/~ubuntu-docviewer-dev/ubuntu-docviewer-app/lo-viewer/view/head:/src/app/qml/loView/LOViewPage.qml