java: fix log string for RemoteTargetLocator#defaultContent

driver.switchTo().defaultContent() used to log the following:

   Executing: [switch to frame: null]

It turns out that the handler SwitchToFrame expects the parameter id to be set to null for switching to the default content.

Signed-off-by: Daniel Davison <[email protected]>

Author: alb-i986

java/server/src/org/openqa/selenium/remote/server/handler/SwitchToFrame.java

@@ -59,6 +59,6 @@ public Void call() throws Exception {
 
   @Override
   public String toString() {
-    return String.format("[switch to frame: %s]", id);
+    return String.format("[switch to frame: %s]", (id == null ? "default" : id));
   }
 }