Hello I defined a documenttype (using uSiteBuilder) and everything works correctly. But if I try to define a new property of type "ContentPicker", I receive a 500 error in runtime. Can anyone help me? You can see the error below

Server Error in '/' Application. Object reference not set to an instance of an object. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.] Vega.USiteBuilder.Util.AddPropertyType(IContentTypeBase contentType, DataTypeDefinition dt, String alias, String name, String tabName) +41 Vega.USiteBuilder.ManagerBase.SynchronizeContentTypeProperties(Type typeContentType, IContentType contentType, DocumentTypeAttribute documentTypeAttribute, Boolean& hadDefaultValues, Boolean updateMixins) +613 Vega.USiteBuilder.DocumentTypeManager.SynchronizeDocumentType(Type typeDocType, Type baseTypeDocType) +934 Vega.USiteBuilder.DocumentTypeManager.SynchronizeDocumentTypes(Type baseTypeDocType) +114 Vega.USiteBuilder.DocumentTypeManager.Synchronize() +461 Vega.USiteBuilder.UmbracoManager.Synchronize() +159 Vega.USiteBuilder.UmbracoManager.SynchronizeIfNotSynchronized() +127 System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +138 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +90