I try to create a new media folder below an excisting media folder but when I click on the Create button the next error appears:

The complete error: 

At /umbraco/create.aspx?nodeID=1035808&nodeType=media&nodeName=Test&rnd=83.5&rndo=83.7 (Referred by: 
https://intranet.prismanet.nl/umbraco/create.aspx?nodeID=1035808&nodeType=media&nodeName=Test&rnd=83.5&rndo=83.7):
 System.Data.SqlTypes.SqlNullValueException: Data is Null. This method or property cannot be called on Null 
values.     at System.Data.SqlClient.SqlBuffer.get_Int32()     
at umbraco.DataLayer.RecordsReaderAdapter`1.GetInt(String fieldName) in 
d:\TeamCity\buildAgent\work\7380c184e9fcd3ea\umbraco\datalayer\RecordsReaderAdapter.cs:line 285     
at umbraco.cms.businesslogic.web.Document.GetMaxDocumentSortOrder(Int32 parentId, Guid objectType)     
at umbraco.cms.businesslogic.CMSNode.MakeNew(Int32 parentId, Guid objectType, Int32 userId, Int32 level, 
String text, Guid uniqueID)     at umbraco.cms.businesslogic.media.Media.MakeNew(String Name, MediaType dct, 
User u, Int32 ParentId)     at umbraco.mediaTasks.Save()     
at umbraco.presentation.create.dialogHandler_temp.Create(String NodeType, Int32 TypeId, Int32 NodeId, String Text)
     at umbraco.cms.presentation.create.controls.media.sbmt_Click(Object sender, EventArgs e)     
at System.Web.UI.WebControls.Button.OnClick(EventArgs e)     
at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)     
at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)     
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, 
Boolean includeStagesAfterAsyncPoint)

Does anyone have any clue as to what might be wrong?

Cheers,

Sander