Fixed device conversion method

[bendboaz]

Fixes #886

Description:
Fixed bug from #886 where device #0 was considered "None" and no conversion was performed.
Three words added to the code overall, so no tests/docs added.

Check list:

• New tests are added (if a new feature is added)
• New doc strings: description and/or example code are in RST format
• Documentation is updated (if required)

[vfdev-5]

@bendboaz thanks for the PR!
Thinking more on the snippet of #886 it seems like passing device as int is a legacy usage : https://pytorch.org/docs/stable/tensor_attributes.html#torch.torch.device

However, explicit checking of device is None is OK.

[bendboaz]

Definitely, and my fix for this (in my code, not in the PR) was actually moving to the correct definition of devices. Anyways, you're right on both accounts :)

P.s really excited, that's my first time adding to an OS project. Thanks for the great work!