trust object type and avoid dynamic_cast due to cross-library RTTI trouble.

ObjectTypes/HexahedralMesh/PluginFunctionsHexahedralMesh.cc

@@ -108,7 +108,7 @@ bool getObject( int _identifier, HexahedralMeshObject*& _object ) {
   BaseObjectData* object = 0;
   PluginFunctions::getObject(_identifier,object);
 
-  _object = dynamic_cast< HexahedralMeshObject* >(object);
+  _object = object ? hexahedralMeshObject(object) : nullptr;
   return ( _object != 0 );
 }
 
@@ -120,7 +120,7 @@ bool getObject( int _identifier, HexahedralMeshObject*& _object ) {
 HexahedralMesh* hexahedralMesh( BaseObjectData* _object ) {
 
   if ( _object->dataType(DATA_HEXAHEDRAL_MESH) ) {
-    HexahedralMeshObject* object = dynamic_cast< HexahedralMeshObject* >(_object);
+    HexahedralMeshObject* object = static_cast< HexahedralMeshObject* >(_object);
     return object->mesh();
   } else
     return 0;
@@ -139,7 +139,7 @@ HexahedralMesh* hexahedralMesh( int _identifier ) {
 HexahedralMeshObject* hexahedralMeshObject( BaseObjectData* _object ) {
   if ( ! _object->dataType(DATA_HEXAHEDRAL_MESH) )
     return 0;
-  return dynamic_cast< HexahedralMeshObject* >( _object );
+  return static_cast< HexahedralMeshObject* >( _object );
 }