Fix #56 - LINC selfcal crash in latest master (and latest singularity image)

workflows/linc_target.cwl

@@ -241,7 +241,7 @@ steps:
         source: 
           - num_SBs_per_group
           - selfcal
-        valueFrom: '$(self[0] == null ? (self[-1] ? -1 : null) : self[0])'
+        valueFrom: '$(self[0] == null ? (self[1] ? -1 : null) : self[0])'
       - id: reference_stationSB
         source: reference_stationSB
       - id: filter_baselines