Locker Field Search "Is-Null" True or False returns HTTP 500 Error

We are unable to search the locker using the "Is-Null" Search term. This issue occurs across all environments that I have checked so far.
This search terms works well in Connectors and Adaptors and would be extremely useful for lockers as well.
Any attempt to use the Is-Null Search term in a locker returns the following error:

System.AggregateException: One or more errors occurred. ---> Unify.Framework.Client.SwaggerException: The HTTP status code of the response was not expected (500).
at Unify.Connect.Web.Client.LockerEntityClient.<SearchEntitiesAsync>d__11.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Unify.Connect.Web.Client.ProfiledLockerEntityClient.<SearchEntitiesAsync>d__4.MoveNext()
--- End of inner exception stack trace ---
at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)
at Unify.Connect.Web.LockerController.InnerRetrievalToResults[TResult](EntityRetrievalInformation`1 retrievalInformation, Func`3 getResults)
at Unify.Connect.Web.LockerController.LockerEntities(EntityRetrievalInformation`1 information)
at Unify.Connect.Web.LockerController.<LockerEntityData>d__65.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at lambda_method(Closure , Task )
at System.Web.Mvc.Async.TaskAsyncActionDescriptor.EndExecute(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass34.<BeginInvokeAsynchronousActionMethod>b__33(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3c()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass45.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3e()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass1e.<>c__DisplayClass28.<BeginInvokeAction>b__19()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass1e.<BeginInvokeAction>b__1b(IAsyncResult asyncResult)
---> (Inner Exception #0) HTTP Response: {"Message":"An error has occurred.","ExceptionMessage":"Illegal operator '==' at 'Unify.Product.IdentityBroker.FilterInformation'. The supported operators are: 'true, false'.","ExceptionType":"System.NotSupportedException","StackTrace":" at Unify.Connect.Web.IdentifierEntitySearchUtilityBase`2.GenerateSearchFunction(FilterInformation searchInformation, Lazy`1 schema)\r\n at Unify.Product.IdentityBroker.DefaultEntityControllerFilterCondition`1.Apply(FilterInformation information, IEnumerable`1 entities)\r\n at Unify.Product.IdentityBroker.EntityControllerSearchFilter`2.ApplyFilter(IEnumerable`1 entities, FilterInformation filterInformation, Guid partitionId)\r\n at Unify.Product.IdentityBroker.EntityControllerSearchFilter`2.<>c__DisplayClass7_0.<ApplyFilter>b__0(IEnumerable`1 filtered, FilterInformation filter)\r\n at System.Linq.Enumerable.Aggregate[TSource,TAccumulate](IEnumerable`1 source, TAccumulate seed, Func`3 func)\r\n at Unify.Product.IdentityBroker.EntityControllerSearchFilter`2.ApplySearch(SearchInformation searchInformation, IEnumerable`1 entities, Guid partitionId)\r\n at Unify.Product.Plus.LockerEntityController.SearchEntities(Guid partitionId, SearchInformation searchInformation)\r\n at lambda_method(Closure , Object , Object[] )\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass10.<GetExecutor>b__9(Object instance, Object[] methodParameters)\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Filters.AuthorizationFilterAttribute.<ExecuteAuthorizationFilterAsyncCore>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()"} Unify.Framework.Client.SwaggerException: The HTTP status code of the response was not expected (500).
at Unify.Connect.Web.Client.LockerEntityClient.<SearchEntitiesAsync>d__11.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Unify.Connect.Web.Client.ProfiledLockerEntityClient.<SearchEntitiesAsync>d__4.MoveNext()<---