bugzilla 38431: description of attribute failonerror in sync task

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@442004 13f79535-47bb-0310-9956-ffa450edef68

docs/manual/CoreTasks/sync.html

@@ -46,7 +46,7 @@ dir, it will get removed from the target.</p>
   </tr>
   <tr>
     <td valign="top">failonerror</td>
-     <td valign="top">Log a warning message, but do not stop the build,
+     <td valign="top">If is set to false, log a warning message, but do not stop the build,
        when one of the nested filesets points to a directory that
        doesn't exist.
      </td>