'free(): invalid pointer' printed in verification process

[nyanmn]

I have the following versions installed.

ubuntu 20
mmcv version is 1.7.1
mmdet version is 2.28.0
mmtrack version is 0.14.0.

Running demo for verification gives me

Warning: The model doesn't have classes
[>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>] 8/8, 3.8 task/s, elapsed: 2s, ETA:     0smaking the output video at mot.mp4 with a FPS of 3
[>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>] 8/8, 32.6 task/s, elapsed: 0s, ETA:     0s
free(): invalid pointer
Aborted (core dumped)

What could be wrong with the last two lines?