Could not export coco keypoints when keyframe and outside set to true

[Yeek020407]

Actions before raising this issue

• I searched the existing issues and did not find anything similar.
• I read/searched the docs

Steps to Reproduce

1. annotate the first frame with skeleton track
2. set the third frame as keyframe
3. set the fifth frame with switch outside
4. Will see ValueError: operands could not be broadcast together with shapes (0,) (4,)

Expected Behavior

Successfully export coco keypoints annotations

Possible Solution

No response

Context

No response

Environment

- tested on https://app.cvat.ai/

[Yeek020407]

I discovered this issue while doing this PR. I am currently solving this issue. Could you assign this to me?

[Drise13]

I think I've run into the same issue, @zhiltsov-max and I were discussing on the PR but we are moving here since I think this is more to the point of the issue. I have this json backup file from localhost:8080/api/jobs/10/annotations?scheme=json.
annotations.json

This file has several skeleton tracked shapes both with and without points. When trying to export, it tried to interpolate the skeleton shapes and throws the broadcast error identified above: ValueError: operands could not be broadcast together with shapes (0,) (4,).

My intuition tells me that skeleton tracks should not try to be interpolated and only use the points, since the skeleton is simply a "composite annotation". That seems to work correctly when I cleaned out the skeletons with no points.

I have a workaround mentioned here: #7669 (comment).