Obligatory Annotation (or junk image)

[joergGros]

Is your feature request related to a problem? Please describe.
When switching between images in SIA, new ones are automatically treated as labeled, even though there is no annotation (for example when drawing polygons). I can see, that the progress bar immediately fills, as I go back to an old image.

Describe the solution you'd like
My idea would be an option which can be triggered during pipeline-creation, "obligatory annotation". If set to true, an image would only be marked as already finished when there is at least one annotation (or the image is marked as junk).