It is simply missing data. When you are processing hundreds of images and using an external data as the source of your code replacements, it is not unusual for a field to be missing occasionally.
In my case I am posting photos for sale of ski racers. I take the race results (which includes things like name, racer ID number/license, team, age, race class, gender, bib number, their time in the race, and how they placed). Sometimes the racer does not have an ID number, so this is blank. If the racer is disqualified, then they have no time nor place.
I process all the data in Excel and then export a CR text file. For maintenance reasons, I try to keep my Excel code as simple as possible, and therefore I would prefer to continue exporting the CR in the format I have described in my previous posts. Alternatively, I could recode my worksheet and take more control of how the missing fields were represented.
This is not a high priority concern for me, just something I thought was worth bringing to your attention.
Deven