The driver is supposed to ignore it as per the spec, but let's be
conservative and pass the value defined by the spec.

Leave it as invalid for approximate (floating-point) datatypes.

Change-Id: I542fdde5e711a335c708ad9e6f2abe2fd8632ef6
Reviewed-on: https://gerrit.libreoffice.org/20685Reviewed-by: Lionel Elie Mamane <lionel@mamane.lu>
Tested-by: Lionel Elie Mamane <lionel@mamane.lu>