Move logging message after vertex check

When creating the list, we may have fewer than needed vertices, which
prevents calculating the area

(cherry picked from commit 6c05f2c67c)

libs/kimath/include/geometry/polygon_triangulation.h

@@ -81,11 +81,11 @@ public:
         /// therefore cannot be polygons
         VERTEX* firstVertex = createList( aPoly );
 
-        wxLogTrace( TRIANGULATE_TRACE, "Created list with %f area", firstVertex->area() );
-
         if( !firstVertex || firstVertex->prev == firstVertex->next )
             return true;
 
+        wxLogTrace( TRIANGULATE_TRACE, "Created list with %f area", firstVertex->area() );
+
         firstVertex->updateList();
 
         /**