AOI not really intersecting S1 scenes

[loreabad6]

For several areas we have had the cases that the AOI does not really overlap the scenes of interest, see example below.
This could be a problem of the metadata during querying, checking of the geographic location of the scenes using stsa or a matter of nodata at the edge of a scene.
The problem is obvious when checking the results but not during the process. We should make sure that the subsetting step checks if there is any data other than no data inside the created file (P2_subset), before going on with the unwrapping (which fails for obvious reasons).
I am not sure if we can catch this error earlier since quite some computation power is already invested to this point.
Also linked to #9