bail early for empty search content

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@540164 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/types/selectors/ContainsSelector.java

@@ -163,7 +163,7 @@ public class ContainsSelector extends BaseExtendSelector implements ResourceSele
         // throw BuildException on error
         validate();
 
-        if (r.isDirectory()) {
+        if (r.isDirectory() || contains.length() == 0) {
             return true;
         }