ASP.Net throws an error but still posts the data - asp.net

Question

We are making a movie rating web application but we come across the error Object reference not set to an instance of an object. even though we get that error when we navigate back to the ratings page the rating got added.
Contoller:
public ActionResult RateMedia(string Item, int Rate)
{
PopMediaDDL();
var userStore = new UserStore<ApplicationUser>(ldb);
var manager = new UserManager<ApplicationUser>(userStore);
var user = manager.FindById(User.Identity.GetUserId());
MediaRating rate = new MediaRating();
rate.Title = ldb.MediaData.First(c => c.MediaName == Item);
rate.Rating = Rate;
rate.RateFor = user;
ldb.MediaRatingData.Add(rate);
ldb.SaveChanges();
return View();
}
Model:
public class MediaRating
{
[Key]
public int MediaRatingID { get; set; }
public virtual ApplicationUser RateFor { get; set; }
public virtual Media Title { get; set; }
public int Rating { get; set; }
}
View:
#using CollectionCompanion.Extensions
#using CollectionCompanion.Models;
#model CollectionCompanion.Models.UserCollectionItem
<h2>Rate Media!</h2>
<hr />
#using (Html.BeginForm())
{
<div style="width:80%;">
<div id="AddColItem">
#Html.AntiForgeryToken()
#Html.TextBoxFor(m => m.Item, new { #id = "MediaItem",#style= "color:black;", #name = "MediaItem", #class = "form-control" })
</div>
<div id="AddColDD">
<select id="Rate" name="Rate">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
</div>
<div id="AddColBTN">
<input type="hidden" name="UserCollection" value="#ViewBag.UserCollectionID" />
<button type="submit" class="btn btn-default btn-info"><span class="glyphicon glyphicon-plus"></span> Add</button>
</div>
</div>
}
#foreach (MediaRating rating in ViewBag.Ratings)
{
<div>
<div style="width:50%;">
#rating.Title.MediaName
</div>
<div style="width:50%">
#rating.Rating
</div>
</div>
}
<script type="text/javascript">
$("#MediaItem").autocomplete({
change: function (event, ui) { },
source: "../../Media/GetMediaResult/",
minLength: 2
}
);
</script>

Answer 1

You are returning the view without a model at the end of your controller action:
return View();
I suspect that you are getting a null reference exception because you're not providing the model nor the ViewBag required to populate the View. It should look similar to the HttpGet controller action as that is providing everything required to build the View in the first place.