mongodb crashing on node app while multiple request

in my node app mongoDB throwing an error for a route only some times.

this is my route:

app.get("/categories/:catName", async function(req, res) {
    const name = req.params.catName;
    console.log(name);
    var catItem;

    await Category.findOne({ name: name }, function(err, foundItem) {
        if (err) {
            console.log(err);
        } else {
            catItem = foundItem;

        }
    });
    await Product.find({ category: catItem._id }, function(err, foundItems) {
        if (err) { console.log(err) } else {
            res.render("category.ejs", { category: catItem, products: foundItems });
            
        }
    });
});

when I start my server and get data from this rouut for the first time everything is working fine. but when I going back and coming to the same route again I am getting an error as follows;

(node:24464) UnhandledPromiseRejectionWarning: TypeError: Cannot read property '_id' of undefined
    at D:\DEV\WEB\craftyscale\app.js:58:44
    at processTicksAndRejections (internal/process/task_queues.js:93:5)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:24464) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:24464) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

what is going wrong here? can someone help me.