GraphQL mutation for file upload does not work.

Steps:

1. Execute request (link to doc)

   mutation CreateImage($file: FileUpload!) {
     createImage(
       parentLocationId: 51,
       language: eng_GB,
       input: {
         name: "An image created over GraphQL",
         image: {
           alternativeText: "The alternative text",
           file: $file
         }
       }
     ) {
       _contentInfo { id mainLocationId }
       name
       image { fileName alternativeText uri }
     }
   }
   

Actual result: Image content item is created but error response is returned:

{
  "errors": [
    {
      "debugMessage": "Call to undefined method Ibexa\\Core\\Repository\\Values\\Content\\Content::getContentInfo()",
      "message": "Internal server Error",
      "extensions": {
        "category": "internal"
      },
      "locations": [
        {
          "line": 17,
          "column": 5
        }
      ],
      "path": [
        "createImage",
        "_contentInfo"
      ],
      "trace": [
        { ...

Expected result: Image is created and file is uploaded without errors.