resolves a shitload of warnings like

warn:legacy.osl:941:1:xmloff/source/forms/elementimport.cxx:426: OElementImport::implImportGenericProperties: unsupported value type!
warn:legacy.osl:941:1:xmloff/source/forms/elementimport.cxx:443: OElementImport::EndElement: could not set the property "ObjIDinMSO"!
warn:legacy.osl:941:1:xmloff/source/forms/elementimport.cxx:444: caught an exception!
in function:void xmloff::OElementImport::implApplyGenericProperties()
type: com.sun.star.lang.IllegalArgumentException

Change-Id: Ia598d12e7d9429fe4ad3b1e7173e11e75060a613