Merchant Profile image upload fails

[HoelShare]

Currently it's not possible to upload an image via /merchant-api/v1/profile/media
Return:

{
  "errors": [
    {
      "status": "500",
      "code": "STOREFRONT__MEDIA_ILLEGAL_FILE_TYPE",
      "title": "Internal Server Error",
      "detail": "Type \"image\/jpeg\" of provided file is not allowed for images",
      "meta": {
        "parameters": {
          "mimeType": "image\/jpeg",
          "uploadType": "images"
        }
      }
    }
  ]
}

The error is thrown by the Shopware\Storefront\Framework\Media\Validator\StorefrontMediaImageValidator the UploadedFile->getExtension (line Shopware\Storefront\Framework\Media\Validator\MimeTypeValidationTrait::14) Function returns empty string.