Sending detection measurements only if detection are present on the image

[Rdornier]

When sending Annotations to OMERO, the menu gives the option to send Detection measurments on OMERO.
If this box is ticked, and if there is no detections on theimage, then the detection measurment is still send to OMERO, but the file empty (only headers).

In order to not pile-up a lot of empty files and to keep the database as clean as possible, I think it is a good idea to not send detection measurements if there are no detections. This behavor can also be applied when we try to send annotations measurment without any annotations on the image.

In such case, maybe having a warning notification to inform the users can be a good idea as well.