JNI-160: close() on obj with handle == 0 does nothing (no decrement either)

src/codegen/gen_java_Message.ysl2

@@ -69,10 +69,12 @@ tstylesheet {
                 }
 
                 public final void close() {
+                    if(handle != 0) {
                         release(handle);
                         handle = 0;
                         instanceCount--;
                     }
+                }
 
                 public static int getInstanceCount() {
                     return instanceCount;