Don't execute the implict target if no default available.

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@273776 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -606,8 +606,6 @@ public class Main {
                 if (targets.size() == 0) {
                     if (project.getDefaultTarget() != null) {
                         targets.addElement(project.getDefaultTarget());
-                    } else {
-                        targets.addElement(""); // implicit target
                     }
                 }