setting up default images on a restful routes create route - node.js

Question

I am relatively new to coding and have been working on a restful routes exercise for an online course using a MEN stack. In the exercise, I am trying to use a default image when no data is entered into the /new route form. I have already indicated a default image in my mongoose schema, but it doesn't seem to be working when I leave the image field blank on my form. It creates a new post with a "unknown" src attribute. I have attached code for my schema, my /new ejs form, and new and create routes. Thanks for any help!
(MONGOOSE SCHEMA)
var catSchema = new mongoose.Schema({
name : String,
description: String,
ranking: Number,
image: {type: String, default: "https://i.cubeupload.com/SnsWs2.png"},
created: {type:Date, default: Date.now}
(NEW AND CREATE ROUTES)
app.post("/cats", function(req,res){
Cat.create(req.body.cat, function(err,newBlog){
if(err){
res.redirect("/cats/new")
}else{
res.redirect("/cats")
}
});
});
(NEW ROUTE)
<%- include("partials/header") %>
<div class="container">
<form action="/cats" method="POST">
<div class="form-group">
<label required for="cat[name]">Name</label>
<input type="text" name="cat[name]" class="form-control" id="name" aria-describedby="emailHelp" placeholder="Enter cat name">
</div>
<div class="form-group">
<label for="cat[description]">Description</label>
<input type="text" class="form-control" name="cat[description]" placeholder="description">
</div>
<div class="form-group">
<label for="cat[ranking]">Ranking</label>
<input type="number" class="form-control" name="cat[ranking]" placeholder="Password">
</div>
<div class="form-group">
<label for="cat[image]">Ranking</label>
<input type="text" class="form-control" name="cat[image]" placeholder="image URL">
</div>
<button type="submit" class="btn btn-primary">Submit</button>
</form>
</div>