NullReferenceException: Object reference not set to an instance of an object.
at Asparona.UI.Controllers.CourseController.<>c.b__7_4(CourseDetails x) in E:\Teamcity\BuildAgent\work\1fc4bebba1e6fa42\Asparona.UI\Controllers\CourseController.cs:line 57 at System.Linq.Lookup`2.Create[TSource](IEnumerable`1 source, Func`2 keySelector, Func`2 elementSelector, IEqualityComparer`1 comparer) at System.Linq.GroupedEnumerable`3.GetEnumerator() at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext() at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection) at Solutionists.MP.Infrastructure.Web.ListExtensions.ToSelectList[T](IEnumerable`1 values, Func`2 value, Func`2 text, Predicate`1 selectedItem, Boolean includeEmptyOption, String emptyOptionDisplayText) in e:\Teamcity\BuildAgent\work\c5bd4e46da0deed3\Solutionists.MP.Infrastructure\Web\ListExtensions.cs:line 0 at Asparona.UI.Controllers.CourseController.PopulateAvailableFilters(CourseByDateParameterViewModel requestViewModel, List`1 courseList, CourseByDateResultViewModel resultViewModel) in E:\Teamcity\BuildAgent\work\1fc4bebba1e6fa42\Asparona.UI\Controllers\CourseController.cs:line 56 at Asparona.UI.Controllers.CourseController.CoursesByDate(CourseByDateParameterViewModel requestViewModel) in E:\Teamcity\BuildAgent\work\1fc4bebba1e6fa42\Asparona.UI\Controllers\CourseController.cs:line 71 at lambda_method(Closure , ControllerBase , Object[] ) at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) at System.Web.Mvc.Async.AsyncControllerActionInvoker.b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.b__3d() at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass46.b__3f() at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.<>c__DisplayClass2b.b__1c() at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass21.b__1e(IAsyncResult asyncResult)