Fixed two issues with GT annotations

[bsekachev]

Motivation and context

1. When there are conflicts on the first frame, they are not highlighted properly if CHANGE_FRAME_SUCCESS is not fired yet
2. UI crash if to hide some annotations related to a conflict and hover mouse over the conflict

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 #7299 (8ad3c0d) into develop (fb610a4) will increase coverage by 0.00%.
Report is 3 commits behind head on develop.
The diff coverage is 43.75%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #7299   +/-   ##
========================================
  Coverage    82.93%   82.94%           
========================================
  Files          372      372           
  Lines        39576    39570    -6     
  Branches      3688     3688           
========================================
- Hits         32824    32821    -3     
+ Misses        6752     6749    -3     

Components	Coverage Δ
cvat-ui	78.39% <43.75%> (+<0.01%)	⬆️
cvat-server	87.10% <ø> (+<0.01%)	⬆️