Topic on Extension talk:TimedMediaHandler

I installed TimedMediaHandler with latest version. but when I upload a mp4 file, I received below error. There are no problem to upload a jpeg file. Could help me solve this problem?

[93b9cad69e1e225a65fe86a1] /Special:Upload Error from line 1091 of /var/www/mediawiki/includes/specials/SpecialUpload.php: Call to a member function getUrl() on boolean Backtrace:

1. 0 /var/www/mediawiki/includes/specials/SpecialUpload.php(893): UploadForm->getDescriptionSection()
2. 1 /var/www/mediawiki/includes/specials/SpecialUpload.php(267): UploadForm->__construct(array, DerivativeContext, MediaWiki\Linker\LinkRenderer)
3. 2 /var/www/mediawiki/includes/specials/SpecialUpload.php(446): SpecialUpload->getUploadForm(string, string, boolean)
4. 3 /var/www/mediawiki/includes/specials/SpecialUpload.php(519): SpecialUpload->showUploadWarning(array)
5. 4 /var/www/mediawiki/includes/specials/SpecialUpload.php(209): SpecialUpload->processUpload()
6. 5 /var/www/mediawiki/includes/specialpage/SpecialPage.php(522): SpecialUpload->execute(NULL)
7. 6 /var/www/mediawiki/includes/specialpage/SpecialPageFactory.php(576): SpecialPage->run(NULL)
8. 7 /var/www/mediawiki/includes/MediaWiki.php(283): SpecialPageFactory::executePath(Title, RequestContext)
9. 8 /var/www/mediawiki/includes/MediaWiki.php(851): MediaWiki->performRequest()
10. 9 /var/www/mediawiki/includes/MediaWiki.php(512): MediaWiki->main()
11. 10 /var/www/mediawiki/index.php(43): MediaWiki->run()
12. 11 {main}

This means that the server was unable to generate a thumbnail preview for this image for some reason.

Probably something is wrong with the ffmpeg or the likes. It shouldn't crash on it of course. I filed ticket phab:T155771 for the crash.