erp5_svg_editor: add method-draw canvg missing files

bt5/erp5_svg_editor/SkinTemplateItem/portal_skins/erp5_svg_editor/method-draw/lib/canvg.xml

@@ -6,6 +6,12 @@
     </pickle>
     <pickle>
       <dictionary>
+        <item>
+            <key> <string>_objects</string> </key>
+            <value>
+              <tuple/>
+            </value>
+        </item>
         <item>
             <key> <string>id</string> </key>
             <value> <string>canvg</string> </value>