Add missing initialization of existing_org in organizations selector.

Without this initialization the organizations selector doesn't select the current organization.

ckan/templates/package/snippets/package_basic_fields.html

@@ -65,6 +65,7 @@
 {% endif %}
 
 {% if show_organizations_selector %}
+  {% set existing_org = data.owner_org %}
 <div class="control-group">
   <label for="field-organizations" class="control-label">{{ _('Organization') }}</label>
   <div class="controls">