OOXMLFastContextHandlerShape::sendShape() deletes the parent context's
ShapeTypeContext::mrTypeModel.

It looks like the sendShape() can't be delayed because writerfilter
wants to import the v:textbox content into a text frame.

Keep the shape alive until the end of the containing context.

Not sure if it's going to process the v:fill element properly,
but at lest valgrind is happy.

(probably regression from CWS writerfilter32bugfixes01)

Change-Id: Ifeab84751a1b20b2f272c4dd74b7097deb5eece0