Don't use getReference in <isreference> unless really required. PR 44822.

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@710086 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -1962,6 +1962,15 @@ public class Project implements ResourceFactory {
         return references;
     }
 
+    /**
+     * Does the project know this reference?
+     *
+     * @since Ant 1.8.0
+     */
+    public boolean hasReference(String key) {
+        return references.containsKey(key);
+    }
+
     /**
      * Look up a reference by its key (ID).
      *

src/main/org/apache/tools/ant/taskdefs/condition/IsReference.java

@@ -62,13 +62,13 @@ public class IsReference extends ProjectComponent implements Condition {
                                      + "condition");
         }
 
-        Object o = getProject().getReference(ref.getRefId());
-
-        if (o == null) {
+        String key = ref.getRefId();
+        if (!getProject().hasReference(key)) {
             return false;
         } else if (type == null) {
             return true;
         } else {
+            Object o = getProject().getReference(key);
             Class typeClass =
                 (Class) getProject().getDataTypeDefinitions().get(type);