message: Make Entropy work and also fix a bug in the loop
diff: @@ -416,9 +416,12 @@ class Entropy(BaseEstimator, TransformerMixin):
  new_X = BirthPersistenceTransform().fit_transform(X)
  for i in range(num_diag):
  -
  orig_diagram, diagram, num_pts_in_diag = X[i], new_X[i], X[i].shape[0]
  + try:
  new_diagram = DiagramScaler(use=True, scalers=[([1], MaxAbsScaler())]).fit_transform([diagram])[0]
  + except ValueError:
  + # Empty persistence diagram case - https://github.com/GUDHI/gudhi-devel/issues/507
  + new_diagram = np.empty(shape = [0, 2])
  if self.mode == "scalar":
  ent = - np.sum( np.multiply(new_diagram[:,1], np.log(new_diagram[:,1])) )
  @@ -436,8 +439,7 @@ class Entropy(BaseEstimator, TransformerMixin):
  ent = ent / np.linalg.norm(ent, ord=1)
  Xfit.append(np.reshape(ent,[1,-1]))
  - Xfit = np.concatenate(Xfit, 0)
  -
  + Xfit = np.concatenate(Xfit, axis=0)
  return Xfit
  def __call__(self, diag):
  