xml_dom.py: NodeTextEntryIter: Allow empty values through as None, and instead filter them out in TextEntryOnlyIter using new helper function non_empty(). This allows XML functions to decide for themselves whether empty values should be filtered out, because process() will now no longer automatically remove them. This will enable process() to work with SQL functions, which must not have empty values filtered out because this will remove required, but nullable, arguments.
xml_dom.py: NodeTextEntryIter: Allow empty values through as None, and instead filter them out in TextEntryOnlyIter using new helper function non_empty(). This allows XML functions to decide for themselves whether empty values should be filtered out, because process() will now no longer automatically remove them. This will enable process() to work with SQL functions, which must not have empty values filtered out because this will remove required, but nullable, arguments.