ASP.NET GridView not saving when textbox is empty - asp.net

Question

I have a GridView that is editable with an entitydatasource, if my users want to delete the text in one of the fields they cannot. They can replace the text with a space which then saves, but if the textbox is completely empty the save operation doesn't do anything.
How do I combat this?
Thanks
<asp:EntityDataSource ID="EntityDataSource1" runat="server"
ConnectionString="name=CS3Entities" DefaultContainerName="CS3Entities"
EnableFlattening="False" EnableUpdate="True"
EntitySetName="ProductAlertStatuses"
Where="it.AlertType != '0'"
OrderBy="it.Department DESC, it.AlertType DESC"/>
<br/>
<asp:GridView runat="server" ID="ActionPlanGV"
DataSourceID="EntityDataSource1"
OnDataBound="ActionPlanGV_OnRowDataBound"
CssClass="mGrid visibleGrid"
AutoGenerateColumns="False"
DataKeyNames="ProductStatusID">
<Columns>
<asp:TemplateField SortExpression="Department" ItemStyle-CssClass="center">
<HeaderTemplate>
<asp:Label ID="DepartmentColHeader" ToolTip="Moulding or Finishing Department" runat="server" Text="Dept" />
</HeaderTemplate>
<ItemTemplate>
<asp:Label ID="DepartmentColtxt" runat="server" Text='<%# Eval("Department") %>' />
</ItemTemplate>
<ItemStyle CssClass="center"></ItemStyle>
</asp:TemplateField>
<asp:TemplateField SortExpression="AlertType" ItemStyle-CssClass="center">
<HeaderTemplate>
<asp:Label ID="AlertTypeColHeader" ToolTip="Alert Type" runat="server" Text="Alert" />
</HeaderTemplate>
<ItemTemplate>
<asp:Label ID="AlertTypeColtxt" runat="server" Text='<%# ItemDAL.GetAlertStatusColourFromNumber(Eval("AlertType").ToString()) %>' />
</ItemTemplate>
<ItemStyle CssClass="center"></ItemStyle>
</asp:TemplateField>
<%--<asp:BoundField DataField="DateAlertRaised" DataFormatString="{0:d}" HeaderText="Date Alert Raised" ReadOnly="True" SortExpression="DateAlertRaised" />--%>
<asp:TemplateField>
<HeaderTemplate>
<asp:Label ID="ItemIDHeader" ToolTip="Item Code" runat="server" Text="Item" />
</HeaderTemplate>
<ItemTemplate>
<asp:HyperLink ID="ItemID"
runat="server"
Text='<%# Eval("ItemID") %>'
NavigateUrl='<%# Url.GetUrl("ViewItem", Eval("ItemID")) %>' />
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Scrap /Parts" ItemStyle-Width="7%" SortExpression="ActionPlanScrapParts">
<EditItemTemplate>
<asp:TextBox ID="TextBox1" TextMode="MultiLine" Width="75" Height="75" runat="server" Text='<%# Bind("ActionPlanScrapParts") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Bind("ActionPlanScrapParts") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Defect Issue / Description" ItemStyle-Width="15%" SortExpression="ActionPlanDefectDescription">
<EditItemTemplate>
<asp:TextBox ID="TextBox2" TextMode="MultiLine" Width="100" Height="75" runat="server" Text='<%# Bind("ActionPlanDefectDescription") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label2" runat="server" Text='<%# Bind("ActionPlanDefectDescription") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Root Cause" ItemStyle-Width="15%" SortExpression="ActionPlanRootCause">
<EditItemTemplate>
<asp:TextBox ID="TextBox3" TextMode="MultiLine" Width="100" Height="75" runat="server" Text='<%# Bind("ActionPlanRootCause") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label3" runat="server" Text='<%# Bind("ActionPlanRootCause") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Corrective Action<div style='font-size:8px;line-height:8px;'>FN16, FN17, FN03, FN05,<br/>Change Note Number</div>-Who? Due By?" ItemStyle-Width="20%" SortExpression="ActionPlanCorrectiveAction">
<EditItemTemplate>
<asp:TextBox ID="TextBox4" TextMode="MultiLine" Width="100" Height="75" runat="server" Text='<%# Bind("ActionPlanCorrectiveAction") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label4" runat="server" Text='<%# Bind("ActionPlanCorrectiveAction") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Preventative Action<br/>-Who? Due By?" ItemStyle-Width="15%" SortExpression="ActionPlanPreventativeAction">
<EditItemTemplate>
<asp:TextBox ID="TextBox5" TextMode="MultiLine" Width="100" Height="75" runat="server" Text='<%# Bind("ActionPlanPreventativeAction") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label5" runat="server" Text='<%# Bind("ActionPlanPreventativeAction") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Reviewed & Closed" ItemStyle-Width="10%" SortExpression="ActionPlanReviewedClosed">
<EditItemTemplate>
<asp:TextBox ID="TextBox6" TextMode="MultiLine" Width="75" Height="75" runat="server" Text='<%# Bind("ActionPlanReviewedClosed") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label6" runat="server" Text='<%# Bind("ActionPlanReviewedClosed") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Edit" ItemStyle-CssClass="noprint" HeaderStyle-CssClass="noprint">
<EditItemTemplate>
<asp:LinkButton ID="LinkButton1" runat="server" CommandName="Update" Text="Save"/>
<asp:LinkButton ID="LinkButton2" runat="server" CommandName="Cancel" Text="Cancel"/>
</EditItemTemplate>
<ItemTemplate>
<asp:LinkButton ID="lbEdit2" runat="server" CommandName="Edit" Text="Edit"/>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
There is one codebehind method, but that doesn't touch the data:
protected void ActionPlanGV_OnRowDataBound(object sender, EventArgs eventArgs)
{
foreach (GridViewRow row in ActionPlanGV.Rows)
{
var alertTypeColtxt = (Label)row.FindControl("AlertTypeColtxt");
if (alertTypeColtxt != null)
{
if (alertTypeColtxt.Text == "Red")
alertTypeColtxt.Text = "<svg width='18' height='18'><circle cx='9' cy='9' r='8' fill='red' /></svg>";
if (alertTypeColtxt.Text == "Amber")
alertTypeColtxt.Text =
"<svg width='15' height='15'><rect x='0' y='0' height='15' width='15' fill='orange' /></svg>";
if (alertTypeColtxt.Text == "Green")
alertTypeColtxt.Text = "<svg width='18' height='18'><circle cx='9' cy='9' r='8' fill='green' /></svg>";
}
}
}