لماذا قيمة user تساوي null

السلام عليكم.

في المثال التالي.

// Post Schema
const PostSchema = new mongoose.Schema(
  {
    title: {
      type: String,
      required: true,
      trim: true,
      minlength: 2,
      maxlength: 200,
    },
    description: {
      type: String,
      required: true,
      trim: true,
      minlength: 10,
    },
    user: {
      type: mongoose.Schema.Types.ObjectId,
      ref: "User",
      required: true,
    },
    category: {
      type: String,
      required: true,
    },
    image: {
      type: Object,
      default: {
        url: "",
        publicId: null,
      },
    },
    likes: [
      {
        type: mongoose.Schema.Types.ObjectId,
        ref: "User",
      },
    ],
  },
  {
    timestamps: true,
  }
);

// Post Model
const Post = mongoose.model("Post", PostSchema);

الموجه

//  /api/posts/:id
router.get('/:id', validateObjectId, getSinglePostCtr)

الطبقة الوسيطة

module.exports = (req, res, next) => {
    if (!mongoose.Types.ObjectId.isValid(req.params.id)) {
        return res.status(400).json({message: "Invalid Id"})
    }
    next()
}

الدالة

const getSinglePostCtr = asyncHandler(async (req, res) => {
  const post = await Post.findById(req.params.id)
  .populate("user", ["-password"]);
  console.log(post)
  if (!post) {
    return res.status(404).json({ msg: "Post Not Found" })
  }
  res.status(200).json(post);
});

لماذا قيمة user تساوي null

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