Changes to check permissions before either adding writing  or reading segmentations to/from OMERO
Kluge-y attempt to fix error occurring after use of segmentation with OMERO. Really need to understand fully as selected is initialised to 0 so unsure why this code fails on zero
Better attempt to handle the intemittent segmentation manager failure by initialising  n_regions on data_update.
Rein in previous commit to allow segmentation manager to open.