Fixed: a mask becomes visible even if hidden after changing opacity level

[bsekachev]

Motivation and context

How has this been tested?

Checklist

• I submit my changes into the develop branch
• I have created a changelog fragment
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues (see GitHub docs)
• I have increased versions of npm packages if it is necessary
  (cvat-canvas,
  cvat-core,
  cvat-data and
  cvat-ui)

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.

[codecov]

Codecov Report

Merging #7060 (52a51b2) into develop (c6682ff) will decrease coverage by 0.04%.
The diff coverage is 66.66%.

@@             Coverage Diff             @@
##           develop    #7060      +/-   ##
===========================================
- Coverage    82.33%   82.29%   -0.04%     
===========================================
  Files          361      361              
  Lines        39213    39219       +6     
  Branches      3585     3588       +3     
===========================================
- Hits         32286    32277       -9     
- Misses        6927     6942      +15     

Components	Coverage Δ
cvat-ui	77.28% <66.66%> (-0.07%)	⬇️
cvat-server	86.89% <ø> (-0.01%)	⬇️