fixes draw methods for grayscale images

[lgvaz]

closes #806

[codecov]

Codecov Report

Merging #807 (26121c3) into master (0d7f18d) will increase coverage by 0.07%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #807      +/-   ##
==========================================
+ Coverage   87.26%   87.34%   +0.07%     
==========================================
  Files         225      225              
  Lines        4697     4725      +28     
==========================================
+ Hits         4099     4127      +28     
  Misses        598      598              

Flag	Coverage Δ
unittests	87.34% <100.00%> (+0.07%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
icevision/visualize/draw_data.py	89.47% <100.00%> (ø)
icevision/core/tasks.py	100.00% <0.00%> (ø)
icevision/models/mmdet/fastai/callbacks.py	100.00% <0.00%> (ø)
icevision/models/torchvision/fastai/callbacks.py	100.00% <0.00%> (ø)
...sion/models/torchvision/lightning/model_adapter.py	100.00% <0.00%> (ø)
icevision/core/record_components.py	79.47% <0.00%> (+0.06%)	⬆️
icevision/core/mask.py	88.37% <0.00%> (+0.09%)	⬆️
icevision/models/mmdet/lightning/model_adapter.py	96.96% <0.00%> (+0.09%)	⬆️
...sion/tfms/albumentations/albumentations_adapter.py	95.58% <0.00%> (+0.11%)	⬆️
icevision/core/keypoints.py	93.33% <0.00%> (+0.22%)	⬆️
... and 6 more

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[FraPochetti]

I think this can be easily merged.

[lgvaz]

@FraPochetti is this still a thing?

[FraPochetti]

@FraPochetti is this still a thing?

We never got back to it.
Not sure it is relevant actually.

[rbavery]

this seems related: #1080