0021543: EDF 1978 SMESH: Viscous layer for 2D meshes

Avoid dump failure if create a sub-mesh on the main shape
    extracted from it-self

    def Assign(self, algo, mesh, geom):
         ...
-        if not geom:
+        if not geom or geom.IsSame( mesh.geom ):
             self.geom = mesh.geom

src/SMESH_SWIG/smesh_algorithm.py

@@ -195,7 +195,7 @@ class Mesh_Algorithm:
             raise RuntimeError, "Attemp to create " + algo + " algoritm on None shape"
         self.mesh = mesh
         name = ""
-        if not geom:
+        if not geom or geom.IsSame( mesh.geom ):
             self.geom = mesh.geom
         else:
             self.geom = geom