Delegate to Task.perform() instead which has better error checking rather than reimplementing in this class.

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@269713 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/UnknownElement.java

@@ -102,12 +102,7 @@ public class UnknownElement extends Task {
                                      + elementName, location);
         }
 
-        try {
-            project.fireTaskStarted(realTask);
-            realTask.execute();
-        } finally {
-            project.fireTaskFinished(realTask, null);
-        }
+        realTask.perform();
     }
 
     public void addChild(UnknownElement child) {