Do not allow the first file to be missing

Inst_eddies/inst_eddies.py.in

@@ -84,6 +84,14 @@ def loop_inst_eddies(files, bbox, d, my_slice):
     cropped_fname = f"SHPC/Slice_{my_slice}/cropped.nc"
     unpacked_fname = f"SHPC/Slice_{my_slice}/unpacked.nc"
 
+    # First file is out of the loop because it must be present:
+    nc_file = next(files)
+    print("inst_eddies.loop_inst_eddies: Date:", d)
+    print("inst_eddies.loop_inst_eddies: Input file:", nc_file, flush = True)
+    process_1_file(bbox, nco_instance, nc_file, cropped_fname, unpacked_fname,
+                   inst_eddies_exe, d, my_slice, writer)
+    d += 1
+
     for nc_file in files:
         print("inst_eddies.loop_inst_eddies: Date:", d)
         print("inst_eddies.loop_inst_eddies: Input file:", nc_file,