Added a default empty geometry list for mesh2d_get_mesh_boundaries as_polygons() (#223)

* set default value

* simplify test again

Author: veenstrajelmer

meshkernel/meshkernel.py

@@ -1149,7 +1149,8 @@ def get_splines(
         return geometry_list_out
 
     def mesh2d_get_mesh_boundaries_as_polygons(
-        self, geometry_list: GeometryList
+        self,
+        geometry_list: GeometryList = GeometryList(),
     ) -> GeometryList:
         """Retrieves the boundaries of a mesh as a series of separated polygons within the selecting polygon.
            If the polygon is empty, all the mesh boundaries are retrieved.
@@ -1158,7 +1159,7 @@ def mesh2d_get_mesh_boundaries_as_polygons(
         one for the inner boundary and one for the outer boundary.
 
         Args:
-            geometry_list (GeometryList): The selecting polygon.
+            geometry_list (GeometryList, optional): The selecting polygon.
 
         Returns:
             GeometryList: The output network boundary polygon.

tests/test_mesh2d_basics.py

@@ -1121,12 +1121,7 @@ def test_mesh2d_get_mesh_boundaries_as_polygons(meshkernel_with_mesh2d: MeshKern
 
     mk = meshkernel_with_mesh2d(2, 2)
 
-    # Create an empty polygon for selecting all boundaries
-    x_coordinates = np.empty(0, dtype=np.double)
-    y_coordinates = np.empty(0, dtype=np.double)
-    geometry_list_in = GeometryList(x_coordinates, y_coordinates)
-
-    mesh_boundary = mk.mesh2d_get_mesh_boundaries_as_polygons(geometry_list_in)
+    mesh_boundary = mk.mesh2d_get_mesh_boundaries_as_polygons()
 
     assert_array_equal(
         mesh_boundary.x_coordinates,