Error In Page

Error Message: Object cannot be cast from DBNull to other types.

Stack Trace:
System.InvalidCastException: Object cannot be cast from DBNull to other types.
at System.DBNull.System.IConvertible.ToDateTime(IFormatProvider provider)
at Dea.Core.Utilities.GetDate(Object o)
at Dea.MasterCalendar.Events.IcsCreator.CreateIcsString(DataSet outlookPattern, Boolean generateAsTentative, Int32 eventId, Int32 detailId)
at Dea.Web.Sites.MasterCalendar.IcsHelper.GenerateIcs(Int32 eventId, Int32 eventDetailId, DateTime showBookingsFromDate, Boolean generateTentative)
at AddToCal.Page_Load(Object sender, EventArgs e)
at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e)
at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)
at System.Web.UI.Control.OnLoad(EventArgs e)
at Dea.Web.Sites.MasterCalendar.BasePage.OnLoad(EventArgs e)
at System.Web.UI.Control.LoadRecursive()
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Additional Information
ErrorCaughtBy: AddToCal.aspx
PatchNumber: 201711270
ClientName:
Product: