Bug fix: test presence of `radius_4` in reader

We cannot test `"radius4" in shape_rec_outer.record`, as
`shape_rec_outer.record` is not a dictionary. We could test `"radius4"
in shape_rec_outer.record.as_dict()` but it is better to test outside
of the loop in the field names of the shapefile reader object. The bug
comes from commit 83a61016.

Inst_eddies/Analysis/stat.py

@@ -23,6 +23,8 @@ with shapefile.Reader(path.join(args.SHPC, "Slice_0", args.orientation,
      shapefile.Reader(path.join(args.SHPC, "Slice_0", args.orientation,
                                 "outermost_contour")) as outermost_contour:
     n_extr = len(extremum)
+    field_names_outer = [f[0] for f in outermost_contour.fields[1:]]
+    with_radius_4 = 'radius4' in field_names_outer
     
     for rec_extr, shape_rec_outer in zip(extremum.iterRecords(),
                                          outermost_contour):
@@ -35,7 +37,7 @@ with shapefile.Reader(path.join(args.SHPC, "Slice_0", args.orientation,
             
         if shape_rec_outer.record.r_eq_area >= 0: n_outer += 1
 
-        if "radius4" in shape_rec_outer.record:
+        if with_radius_4:
             if shape_rec_outer.record.radius4 == 0:
                 n_radius4[0] += 1
             elif shape_rec_outer.record.radius4 == 1:
@@ -43,7 +45,7 @@ with shapefile.Reader(path.join(args.SHPC, "Slice_0", args.orientation,
             elif shape_rec_outer.record.radius4 >= 2:
                 n_radius4[2] += 1
 
-        if rec_extr.speed == 1e4 and "radius4" in shape_rec_outer.record:
+        if rec_extr.speed == 1e4 and with_radius_4:
             if shape_rec_outer.record.radius4 == 0:
                 n_missing_speed[0] += 1
             elif shape_rec_outer.record.radius4 == 1: