Warning when using --exiftool-merge-keywords and --download-missing

[RhetTbull]

See this Reddit thread.

Running the following command:
osxphotos export --export-by-date --library /Users/turali/Pictures/Photos\ Library.photoslibrary /Volumes/home/Photos --exiftool --sidecar XMP --favorite-rating --exiftool-merge-persons --exiftool-merge-keywords --person-keyword --album-keyword --sidecar-drop-ext --update --export-aae --retry 3 --exportdb ~/.osxphotos_export.db --update-errors --ignore-signature --only-new --verbose --use-photokit --cleanup --download-missing --dry-run

It takes much longer now: the first impression is, it's trying to download everything.

Also, Its showing me the following warning message:

2024-05-29 10:55:27,108 - osxphotos - WARNING - [exifwriter.py](http://exifwriter.py/) - 121 - photo.path is None for photo 710121AD-D951-402A-B56C-4D1BCF607D1F, cannot read exif keyword