fix save_image when height or width == 1

[trougnouf]

This fixes the save_image function when one of the dimensions is one.

Otherwise error is as follow:

Traceback (most recent call last):
  File "run_nn.py", line 250, in <module>
    torchvision.utils.save_image(batch_x.detach().unsqueeze(2).cpu(), "dbg/%s-x.png"%(dbgtitle))
  File "/home/trougnouf/.local/lib/python3.6/site-packages/torchvision/utils.py", line 103, in save_image
    ndarr = grid.mul_(255).add_(0.5).clamp_(0, 255).permute(1, 2, 0).to('cpu', torch.uint8).numpy()
RuntimeError: number of dims don't match in permute

[fmassa]

Thanks for the PR and the fix!

Could you add a test for it in test_utils.py?

[trougnouf]

Done, thank you!

[fmassa]

LGTM!

Just waiting for CI to finish and then this is good to merge!

[codecov-io]

Codecov Report

Merging #1059 into master will increase coverage by 0.11%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1059      +/-   ##
==========================================
+ Coverage   63.83%   63.95%   +0.11%     
==========================================
  Files          66       66              
  Lines        5279     5279              
  Branches      793      793              
==========================================
+ Hits         3370     3376       +6     
+ Misses       1676     1672       -4     
+ Partials      233      231       -2

Impacted Files	Coverage Δ
torchvision/utils.py	65.38% <100%> (+3.84%)	⬆️
torchvision/transforms/functional.py	71.97% <0%> (+1.17%)	⬆️

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