Umbraco Image Pagination Concept Explain

gistfile1.cshtml

@{
  @* Pagination Logic *@
  var postsPerPage = 5;
  
  var allPosts = Model.Content.GetPropertyValue<string>("images").Split(',');
  allPosts.ToList().ForEach(i => i = Umbraco.TypedMedia(i));
  
  var totalPages = Math.Ceiling((double)(allPosts.Count() / (double)postsPerPage));
  
  var currentPageNo = int.Parse(Request.QueryString["p"] ?? "1");
  if (currentPageNo > totalPages) { currentPageNo = 1; }
  
  
  var currentPostsRange = (currentPageNo * postsPerPage) + postsPerPage;
  
  var currentPagePosts = allPosts.Skip((currentPageNo * postsPerPage) - postsPerPage).Take(postsPerPage);

}


<!-- example to output -->
@foreach(var image in allPosts) {
  <img src="image.Url" />
}

Value cannot be null.
Parameter name: source

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.ArgumentNullException: Value cannot be null.
Parameter name: source

Source Error:

Line 6:
Line 7: var allImages = Model.Content.GetPropertyValue<List>("images");
Line 8: var totalPages = Math.Ceiling((double)(allImages.Count() / (double)imagesPerPage));
Line 9:
Line 10: var currentPageNo = int.Parse(Request.QueryString["p"] ?? "1");