That because when the upload path is empty in TinyMCE configuration then global Media ProviderManagerHelper is defaulting to files (previously was images):

We need to check for default folder in the plugin

$defaultPath = ComponentHelper::getParams('com_media')->get('image_path', 'images');
$uploadPath  = $levelParams->get('path', $defaultPath);

I will check later, if no one else will be faster :)

@Fedik I tried with your two lines and adding the use statement but it didnt get the path - dont really understand this code so will leave it to you

Well, it was a bit more complex than that :)
Please test #45956