Remove extraneous comma in line 138 (include for NewContact.tpl)
{elseif $action neq 4}
<td class="label">{ts}With Contact{/ts}</td>
<td class="view-value">
- {include file="CRM/Contact/Form/NewContact.tpl" noLabel=true skipBreak=true multiClient=true parent="activity", showNewSelect=true}
+ {include file="CRM/Contact/Form/NewContact.tpl" noLabel=true skipBreak=true multiClient=true parent="activity" showNewSelect=true}
{if $action eq 1}
<br/>
{$form.is_multi_activity.html} {$form.is_multi_activity.label} {help id="id-is_multi_activity"}