Do not distinguish the case of a single date

I do not see the point any longer of that distinction. If the date
option is used, we could do some checks on the date but not
specifically for the case of a single date in the slice.

Inst_eddies/Analysis/plot_eddy_contours.py

@@ -206,18 +206,12 @@ if __name__ == "__main__":
     if args.window is None: plot_grid_bb(grid_nml, ax)
     SHPC = util_eddies.SHPC_class(args.shpc_dir, def_orient = "Anticyclones")
 
-    if SHPC.get_n_dates(i_slice = 0) == 1:
-        if args.date is not None and args.date != SHPC.d_init[0]:
-            sys.exit("Anticyclones: Bad value of date option")
-
+    if args.date is None:
+        print("No date option, plotting first date of first slice:",
+              SHPC.d_init[0])
         d = SHPC.d_init[0]
     else:
-        if args.date is None:
-            print("No date option, plotting first date:",
-                  SHPC.d_init[0])
-            d = SHPC.d_init[0]
-        else:
-            d = args.date
+        d = args.date
 
     for orientation in ["Anticyclones", "Cyclones"]:
         ishape_list = select_ishapes(d, SHPC, i_slice = 0,