Use the default value in annotations' proxies

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

classpath/avian/AnnotationInvocationHandler.java

@@ -27,6 +27,6 @@ public class AnnotationInvocationHandler implements InvocationHandler {
         return data[i + 1];
       }
     }
-    throw new IllegalArgumentException();
+    return method.getDefaultValue();
   }
 }