exporting with watermark and empty IPTC-fields

Hello!

Export with watermarks works fine. So nice to get all the desired metadates as text.

But only one thing... 😊

Some pics of my collection have a IPTC-title, others do not have an entry on IPTC-title.
When I'm exporting the collection, all these pics without IPTC-titel get a watermark "no title" (german version: "keinTitel").

Any tips to avoid that?
All my pics that have a IPTC-title should get the watermark - all others NOT!!!