Req: Ignore non-geotagged photos when exporting to GE

[rmtk]

When trying to open a batch of photos in Google Earth, I found that one or two non-geotagged photos would make the export impossible (open gps location in google earth button grey out). I had to deselect them manually, which could be inconvinient.

It could be better if Xnview automatically ingore the non-geotagged photos and open only geotagged photos in GE.

[xnview]

See Issue 307 for current status and details.