Problem when using fix_symbolic

[yjdy]

When I try to set automatically or manually set activation functions to be symbolic like hello.ipynb

    self.layer = KAN(width=[dim,2*dim,dim])
    self.layer.fix_symbolic(0,0,0,'sin')
    self.layer.fix_symbolic(0,1,0,'exp')
    self.layer.fix_symbolic(1,0,0,'log')
or

    lib = ['x','exp','log']
    self.layer.auto_symbolic(lib=lib)

I always get the same error:

File "/home/ma-user/anaconda3/envs/xxx/lib/python3.10/site-packages/kan/MultKAN.py", line 947, in fix_symbolic
    x = self.acts[l][:, i]
TypeError: 'NoneType' object is not subscriptable