problem with dropdown listbox exception

[Vaidas Gudas]

I am getting this error:
[ArgumentOutOfRangeException: 'lstAtliko' has a SelectedValue which is
invalid because it does not exist in the list of items.
Parameter name: value]
System.Web.UI.WebControls.ListControl.PerformDataBinding(IEnumerable
dataSource) +970
System.Web.UI.WebControls.ListControl.OnDataBinding(EventArgs e) +80
System.Web.UI.WebControls.ListControl.PerformSelect() +32
System.Web.UI.WebControls.BaseDataBoundControl.DataBind() +99
System.Web.UI.Control.DataBindChildren() +236
System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) +178
System.Web.UI.Control.DataBind() +31
System.Web.UI.Control.DataBindChildren() +236
System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) +178
System.Web.UI.Control.DataBind() +31
System.Web.UI.Control.DataBindChildren() +236
System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) +178
System.Web.UI.Control.DataBind() +31
System.Web.UI.Control.DataBindChildren() +236
System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) +178
System.Web.UI.WebControls.FormView.CreateChildControls(IEnumerable
dataSource, Boolean dataBinding) +3051
System.Web.UI.WebControls.CompositeDataBoundControl.PerformDataBinding(IEnumerable
data) +89
System.Web.UI.WebControls.FormView.PerformDataBinding(IEnumerable data)
+30
System.Web.UI.WebControls.DataBoundControl.OnDataSourceViewSelectCallback(IEnumerable
data) +126
System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments,
DataSourceViewSelectCallback callback) +98
System.Web.UI.WebControls.DataBoundControl.PerformSelect() +154
System.Web.UI.WebControls.BaseDataBoundControl.DataBind() +99
System.Web.UI.WebControls.FormView.DataBind() +23
System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() +92
System.Web.UI.WebControls.FormView.EnsureDataBound() +176
System.Web.UI.WebControls.CompositeDataBoundControl.CreateChildControls()
+100
System.Web.UI.Control.EnsureChildControls() +134
System.Web.UI.Control.PreRenderRecursiveInternal() +109
System.Web.UI.Control.PreRenderRecursiveInternal() +233
System.Web.UI.Control.PreRenderRecursiveInternal() +233
System.Web.UI.Control.PreRenderRecursiveInternal() +233
System.Web.UI.Control.PreRenderRecursiveInternal() +233
System.Web.UI.Page.ProcessRequestMain(Boolean
includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +4437

I know that this value does not exist, but how to catch this error and add
this value to the list by manual