Find the error below, please help me to resolve this issue.

Server Error in '/' Application.

Must specify valid information for parsing in the string. 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.ArgumentException: Must specify valid information for parsing in the string.

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:

[ArgumentException: Must specify valid information for parsing in the string.] System.Enum.TryParseEnum(Type enumType, String value, Boolean ignoreCase, EnumResult& parseResult) +11072070 System.Enum.Parse(Type enumType, String value, Boolean ignoreCase) +78 Umbraco.Forms.Core.FormSettings..ctor() in f:\TeamCity\buildAgent\work\fd622d7f786e1305\Umbraco.Forms.Core\FormSettings.cs:26 Umbraco.Forms.Core.Form.Create() in f:\TeamCity\buildAgent\work\fd622d7f786e1305\Umbraco.Forms.Core\Form.cs:41 Umbraco.Forms.UI.Tasks.FormTasks.Save() in f:\TeamCity\buildAgent\work\fd622d7f786e1305\Umbraco.Forms.UI\Tasks\FormTasks.cs:58 Umbraco.Web.UI.LegacyDialogHandler.Create(HttpContextBase httpContext, User umbracoUser, String nodeType, Int32 nodeId, String text, Int32 typeId) +116 umbraco.presentation.create.dialogHandlertemp.Create(String NodeType, Int32 TypeId, Int32 NodeId, String Text) +121 umbraco.presentation.create.dialogHandlertemp.Create(String NodeType, Int32 NodeId, String Text) +47 Umbraco.Forms.UI.Dialogs.createForm.sbmt_Click(Object sender, EventArgs e) in f:\TeamCity\buildAgent\work\fd622d7f786e1305\Umbraco.Forms.UI\Dialogs\createForm.ascx.cs:31 System.Web.UI.WebControls.Button.OnClick(EventArgs e) +9627994 System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +103 System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10 System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13 System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +35 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1724

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.34249