Cannot upload castopod episodes even after fresh install on new server

Describe the bug

Error when trying to upload podcasts. Fresh server install of debian 11

Steps to reproduce

Try to upload episode

Expected behavior

Episode should upload

Actual behavior

I got an error

Relevant logs and/or screenshots

ErrorException: Undefined array key "extension" in /var/www/castopod/modules/Media/Entities/BaseMedia.php:74
Stack trace:
#0 /var/www/castopod/modules/Media/Entities/BaseMedia.php(74): CodeIgniter\Debug\Exceptions->errorHandler()
#1 /var/www/castopod/modules/Media/Entities/BaseMedia.php(65): Modules\Media\Entities\BaseMedia->initFileProperties()
#2 /var/www/castopod/modules/Media/Entities/Audio.php(29): Modules\Media\Entities\BaseMedia->__construct()
#3 /var/www/castopod/modules/Media/Models/MediaModel.php(112): Modules\Media\Entities\Audio->__construct()
#4 /var/www/castopod/app/Entities/Episode.php(260): Modules\Media\Models\MediaModel->getMediaById()
#5 /var/www/castopod/vendor/codeigniter4/framework/system/Entity/Entity.php(491): App\Entities\Episode->getAudio()
#6 /var/www/castopod/app/Helpers/id3_helper.php(28): CodeIgniter\Entity\Entity->__get()
#7 /var/www/castopod/app/Models/EpisodeModel.php(463): write_audio_file_tags()
#8 /var/www/castopod/vendor/codeigniter4/framework/system/BaseModel.php(1479): App\Models\EpisodeModel->writeEnclosureMetadata()
#9 /var/www/castopod/vendor/codeigniter4/framework/system/BaseModel.php(758): CodeIgniter\BaseModel->trigger()
#10 /var/www/castopod/vendor/codeigniter4/framework/system/Model.php(667): CodeIgniter\BaseModel->insert()
#11 /var/www/castopod/modules/Admin/Controllers/EpisodeController.php(235): CodeIgniter\Model->insert()
#12 /var/www/castopod/modules/Admin/Controllers/EpisodeController.php(63): Modules\Admin\Controllers\EpisodeController->attemptCreate()
#13 /var/www/castopod/vendor/codeigniter4/framework/system/CodeIgniter.php(901): Modules\Admin\Controllers\EpisodeController->_remap()
#14 /var/www/castopod/vendor/codeigniter4/framework/system/CodeIgniter.php(457): CodeIgniter\CodeIgniter->runController()
#15 /var/www/castopod/vendor/codeigniter4/framework/system/CodeIgniter.php(340): CodeIgniter\CodeIgniter->handleRequest()
#16 /var/www/castopod/public/index.php(73): CodeIgniter\CodeIgniter->run()
#17 {main}
```
### Context

- Castopod: 1.3.5 also 1.3.3
- OS: Debian 11 
- Browser: Firefox
- Web server: Apache
- [any other relevant context...]

### Possible fixes

[If you can, link to the line of code that might be responsible for the problem]