`None` parameters not sanitized during pruning
🐛 Bug
ModelPruning callback fails when a module parameter is None. This can happen, for instance,  in a Linear() when bias=False.
Please reproduce using the BoringModel
https://colab.research.google.com/drive/1UApprg-5htIQbosiSyyLLXm1B8wE8EbN?usp=sharing
Expected behavior
Unavailable parameters are already taken care of in sanitize_parameters_to_prune method in ModelPruning callback. A trivial check to ensure the attribute, when present, is not None should solve this. Happy to send a PR.
Environment

CUDA:

GPU:

Tesla K80


available:         True
version:           10.1


Packages:

numpy:             1.19.5
pyTorch_debug:     False
pyTorch_version:   1.8.1+cu101
pytorch-lightning: 1.2.6
tqdm:              4.41.1


System:

OS:                Linux
architecture:

64bit



processor:         x86_64
python:            3.7.10
version:           #1 SMP Thu Jul 23 08:00:38 PDT 2020