Adding A Button To DisplayForm Ribbon For Specific Content Type

I am trying to add a button to the DisplayForm ribbon that appears in its own group on the ribbon for a specific Content Type in SharePoint 2010.

I have the following definition for the group, tab and button.

<?xml version="1.0" encoding="utf-8"?>
<Elements xmlns="http://ift.tt/sQmbje">
<CustomAction
  Id="{9A955843-20D6-400A-A078-C2DE2CBC7861}"
  RegistrationType="ContentType"
  RegistrationId="0x010014D754C688D12A4FB4C811B4B4F67A5C"
  Location="CommandUI.Ribbon.DisplayForm"
  Rights="ViewListItems">
<CommandUIExtension>
  <CommandUIDefinitions>
    <CommandUIDefinition Location="Ribbon.ListForm.Display.Manage.Controls._children">
      <Tab Id="{570EB195-4FF9-4ED4-8ABC-52953C444EBA}"
            Title="MYTAB"
            Description="MY TAB DESCRIPTION"
            Sequence="600">
        <Scaling Id="{C4CD02B6-120F-4868-88A4-2AFBB1F52D80}">
          <MaxSize
              Id="{75AC6A65-7FF2-46D6-B5D1-AE61AD65DF94}"
              Sequence="10"
              GroupId="{7B4A87A5-8047-48AA-81D0-CCD5A5C063A0}"
              Size="Large" />
          <Scale
              Id="{7145A3F1-5087-4A2F-B5E8-55B9A8820974}"
              Sequence="20"
              GroupId="{7B4A87A5-8047-48AA-81D0-CCD5A5C063A0}"
              Size="Large" />
        </Scaling>
        <Groups Id="{F0F9C1D3-34D7-453B-88D1-A3242E8D0D5A}">
          <Group
             Id="{7B4A87A5-8047-48AA-81D0-CCD5A5C063A0}"
             Sequence="10"
             Description="MY GROUP DESCRIPTION"
             Title="MYGROUP"
             Template="MY.Solution.Ribbon.Templates.ExtendedLarge">
            <Controls Id="{1A83D28B-1C26-45E2-89E9-0D38BD6C392A}">
              <Button
               Id="{740DE751-D405-45BC-B38F-134E1A5C6CF0}"
               Alt="SOME ALT TEXT."
               LabelText="MY BUTTON LABEL"
               Image16by16="/_layouts/images/MY.Solution/SomeIcon_16.png"
               Image32by32="/_layouts/images/MY.Solution/SomeIcon_32.gif"
               Command="{E1ABCC91-F6E4-43B6-A159-D043BD534599}"
               Sequence="99"
               TemplateAlias="MY1"
               ToolTipTitle="MY BUTTON TITLE"
               ToolTipDescription="MY BUTTON DESCRIPTION."/>
            </Controls>
          </Group>
        </Groups>
      </Tab>
    </CommandUIDefinition>
    <CommandUIDefinition Location="Ribbon.Templates._children">
      <GroupTemplate Id="MY.Solution.Ribbon.Templates.ExtendedLarge">
        <Layout Title="OneLarge" LayoutTitle="OneLarge">
          <Section Alignment="Top" Type="OneRow">
            <Row>
              <ControlRef DisplayMode="Large" TemplateAlias="MY1" />
            </Row>
          </Section>
        </Layout>
      </GroupTemplate>
    </CommandUIDefinition>
  </CommandUIDefinitions>
  <CommandUIHandlers>
    <CommandUIHandler Command="{E1ABCC91-F6E4-43B6-A159-D043BD534599}" CommandAction="~site/_layouts/MY.Solution/domsomething.aspx?List={ListId}&amp;ID={ItemId}">
    </CommandUIHandler>
  </CommandUIHandlers>
</CommandUIExtension>
</CustomAction>
</Elements>

But I am getting an error after I activate it when I try to view items with a ContentType that this is registered to:

Object reference not set to an instance of an object [NullReferenceException: Object reference not set to an instance of an object.] Microsoft.Web.CommandUI.RibbonRenderer.RenderGroup(DataNode xnGroup, RibbonRenderContext rrc, HtmlTextWriter writer) +1114 Microsoft.Web.CommandUI.RibbonRenderer.RenderTabBody(DataNode xnTab, RibbonRenderContext rrc, HtmlTextWriter writer) +728 Microsoft.Web.CommandUI.RibbonRenderer.RenderRibbon(DataNode xnData, RibbonRenderContext rrc, HtmlTextWriter writer) +5146 Microsoft.Web.CommandUI.Ribbon.AppendRibbon(HtmlTextWriter writer, Boolean headerOnly, UInt32 initialTabScaleIndex, RibbonRenderContext rrc) +76 Microsoft.Web.CommandUI.Ribbon.Render(HtmlTextWriter writer) +1423 Microsoft.SharePoint.WebControls.SPRibbon.Render(HtmlTextWriter writer) +315 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +239 System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer) +252 System.Web.UI.HtmlControls.HtmlForm.Render(HtmlTextWriter output) +86 System.Web.UI.HtmlControls.HtmlForm.RenderControl(HtmlTextWriter writer) +52 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +239 System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +41 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +239 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +239 System.Web.UI.Page.Render(HtmlTextWriter writer) +37 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +4239

I seem to be targeting the correct ContentType because the error is appearing when I view the items associated with that ContentType. But I seem to be missing something in the definition of the Custom Action.

What am I doing wrong?