New Post: Failed to load MultiValueControl control. Value cannot be null.

I have added the Multivaluecontrol to my WIT but I get this error in the field when I try to Preview the template.

Failed to load MultiValueControl control. Value cannot be null. Parameter name: type


Here is my schema
<FIELD name="Triage" refname="Microsoft.VSTS.Common.Triage" type="String" reportable="dimension">

<HELPTEXT>testingmulti select</HELPTEXT>
  <SUGGESTEDVALUES expanditems="false">
  <LISTITEM value="[t1]" />
  <LISTITEM value="[t2]" />
  <LISTITEM value="[t3]" />
  <LISTITEM value="[t4]" />
  </SUGGESTEDVALUES>
 </FIELD>

Here is my form section
<Control Type="MultiValueControl" FieldName="Microsoft.VSTS.Common.Triage" Label="Triag&e:" LabelPosition="Left" />

My files are deployed here:
C:\ProgramData\Microsoft\Team Foundation\Work Item Tracking\Custom Controls\10.0

please help!!