Regression from commit 866a4436 (oox:
handle textboxes in ShapeContextHandler::endFastElement(), 2014-06-04),
the problem was that code in ShapeContextHandler::endFastElement()
assumed that all the XShape implementation it may see provides a TextBox
UNO property (which is specific to Writer) of type bool, but this is not
true.

Fix the problem by assuming false in case it has an other type.

Testcase can be a simple "does it load" one, as in the meantime
exceptions such as trying to read a bool from an uno::Any make the DOCX
XFilter::filter() implementation return false, unlike in the originally
reported LibreOffice 4.4 version that just silently discarded the
remaining content of the document.

Change-Id: I81781a7ec28d085ceee50d386b8eda023f83c29f