Fix mask visualization bug

[vinnamkim]

Summary

• Ticket no. 106161
• Found a bug on visualizing mask while working on Convert class and instance binary masks to COCO instances format #858
• After this patch, mask visualization will working properly as https://github.com/vinnamkim/datumaro/blob/cs/make-coco-instance-mask/notebooks/08_assign_label.ipynb.

How to test

Checklist

• I submit my changes into the develop branch
• I have added description of my changes into CHANGELOG
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below)

# Copyright (C) 2023 Intel Corporation
#
# SPDX-License-Identifier: MIT

[codecov-commenter]

Codecov Report

Patch coverage: 33.33% and project coverage change: -0.02 ⚠️

Comparison is base (94bd96f) 78.59% compared to head (2c349cc) 78.57%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #860      +/-   ##
===========================================
- Coverage    78.59%   78.57%   -0.02%     
===========================================
  Files          199      199              
  Lines        24408    24414       +6     
  Branches      4938     4939       +1     
===========================================
+ Hits         19183    19184       +1     
- Misses        4123     4127       +4     
- Partials      1102     1103       +1     

Flag	Coverage Δ
macos-11_Python-3.8	77.92% <33.33%> (-0.02%)	⬇️
ubuntu-20.04_Python-3.8	78.56% <33.33%> (-0.02%)	⬇️
windows-2019_Python-3.8	78.50% <33.33%> (-0.02%)	⬇️

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

Impacted Files	Coverage Δ
datumaro/components/visualizer.py	91.28% <33.33%> (-2.12%)	⬇️

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