MediaPlayer Cannot read property 'duration' of null - Storybook error

[pietrop]

Describe the bug

as noticed by @emettely when going to MediaPlayer in storybook get error Cannot read property 'duration' of null

To Reproduce
Steps to reproduce the behavior:

1. Go to demo app MediaPlayer https://bbc.github.io/react-transcript-editor/?path=/story/mediaplayer--default
2. See error Cannot read property 'duration' of null - see screenshot below

Expected behavior

Not see an error when looking at MediaPlayer in storybook

Screenshots

in current master

Additional context

Likely to be just to do with initialisation of MediaPlayer component in storybook.

Via @emettely

Original that worked: 9557faa0f66c4abb711301e2fc94fdcd5f48dc4c
Change that introduced bug to story: 45c324dc1dcd2fdd3ca94b1e14a699eab11587e0
so it’s between those two hashes some changes have been introduced