More consistent form_tag macro behavior

flask_admin/templates/admin/lib.html

@@ -116,7 +116,7 @@
     {% endfor %}
 {% endmacro %}
 
-{% macro form_tag() %}
+{% macro form_tag(form=None) %}
     <form action="" method="POST" class="form-horizontal" enctype="multipart/form-data">
       <fieldset>
         {{ caller() }}

flask_admin/templates/admin/model/create.html

@@ -21,7 +21,7 @@
       </li>
 	</ul>
 
-  {% call lib.form_tag() %}
+  {% call lib.form_tag(form) %}
       {{ lib.render_form_fields(form, widget_args=form_widget_args) }}
       {{ lib.render_form_buttons(return_url, extra()) }}
   {% endcall %}

flask_admin/templates/admin/model/edit.html

@@ -8,7 +8,7 @@
 {% endblock %}
 
 {% block body %}
-    {% call lib.form_tag() %}
+    {% call lib.form_tag(form) %}
         {{ lib.render_form_fields(form, widget_args=form_widget_args) }}
         {{ lib.render_form_buttons(return_url) }}
     {% endcall %}