Error: Unable to get value of the property 'getEnumerator': object is null or undefined

Hi,

I am using the javascript client object model.

I am trying to retrieve items in list.

Below is the code used.

function setImage() {

    var clientcontext = new SP.ClientContext.get_current();

    var oweb = clientcontext.get_web();

    var olibrary = oweb.get_lists().getByTitle("DocLibrary");
    var query = new SP.CamlQuery();
    query.set_folderServerRelativeUrl("Lists/DocLibrary/folder1/");

    var folder = olibrary.getItems(query);
   
    clientcontext.load(folder, 'Include(Title,ContentType, FileLeafRef,FileDirRef,File)');

    clientcontext.executeQueryAsync(Function.createDelegate(this, this.RenderDataOnSuccess), Function.createDelegate(this, this.RenderDataOnFailure));
}

function RenderDataOnSuccess() {
   
    var ListEnumerator = this.folder.getEnumerator();
//other code
}

I am getting the error as :  Unable to get value of the property 'getEnumerator': object is null or undefined

How to fix this?

Thanks