Hi,

When trying to add a html button to the TinyMce editors in code, I get an exception in the "All properties" view. The same happens on the Alloy site (v9.6.1).

[ServiceConfiguration(ServiceType = typeof (PropertySettings))]
public class DefaultTinyMceSettings : PropertySettings
{
public DefaultTinyMceSettings()
  {
    DisplayName = "Default Tiny MCE editor";
    Description = "Default Tiny MCE editor settings";
    IsDefault = true;
  }

  public override System.Guid ID
  {
    get { return new System.Guid("a6fe936f-190d-45e2-b83c-ccc0501a7312"); }
  }
}

2016-03-08 08:47:40,967 [11] ERROR EPiServer.Global: 1.2.5 Unhandled exception in ASP.NET
System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.
at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
at EPiServer.Cms.Shell.UI.ObjectEditing.EditorDescriptors.XhtmlStringEditorDescriptor.ModifyMetadata(ExtendedMetadata metadata, IEnumerable`1 attributes)
at EPiServer.Shell.ObjectEditing.ExtensibleMetadataProvider.ApplyExtendersToMetadata(ExtendedMetadata metadata, IEnumerable`1 attributes, IEnumerable`1 metadataHandlers)
at EPiServer.Shell.ObjectEditing.ExtensibleMetadataProvider.GetMetadataForProperties(ExtendedMetadata parent, Object container, Type containerType, IMetadataProvider customProvider)
at EPiServer.Shell.ObjectEditing.ExtendedMetadata.get_Properties()
at EPiServer.Cms.Shell.UI.ObjectEditing.AllowedTypesMetadataExtender.ModifyMetadata(ExtendedMetadata metadata, IEnumerable`1 attributes)
at EPiServer.Shell.ObjectEditing.ExtensibleMetadataProvider.ApplyExtendersToMetadata(ExtendedMetadata metadata, IEnumerable`1 attributes, IEnumerable`1 metadataHandlers)
at EPiServer.Shell.ObjectEditing.ExtensibleMetadataProvider.CreateMetadata(IEnumerable`1 attributes, Type containerType, Func`1 modelAccessor, Type modelType, String propertyName)
at System.Web.Mvc.AssociatedMetadataProvider.GetMetadataForType(Func`1 modelAccessor, Type modelType)
at EPiServer.Shell.UI.Rest.MetadataStore.Get(String id, String modelAccessor)
at lambda_method(Closure , ControllerBase , Object[] )
at System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters)
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.ActionInvocation.InvokeSynchronousActionMethod()
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.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
at System.Web.Mvc.Async.AsyncResultWrapper.End[TResult](IAsyncResult asyncResult, Object tag)
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.AsyncInvocationWithFilters.<>c__DisplayClass46.b__3f()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass33.b__32(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
at System.Web.Mvc.Async.AsyncResultWrapper.End[TResult](IAsyncResult asyncResult, Object tag)
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)
at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
at System.Web.Mvc.Async.AsyncResultWrapper.End[TResult](IAsyncResult asyncResult, Object tag)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult)
at EPiServer.Shell.Services.Rest.RestControllerBase.EndExecute(IAsyncResult asyncResult)
at EPiServer.Shell.Services.Rest.RestHttpHandler.EndProcessRequest(IAsyncResult result)
at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Thanks