### What changes were proposed in this pull request?
When recived active-messages in Pregel, we only need an action operator here and active-messages are not empty, so we don’t need to use count, it’s better to use isEmpty.
### Why are the changes needed?
In the case of 10+ billions of vertices and edges, it will make the speed faster.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
Pass existed tests.
Closes#33648 from StefanXiepj/SPARK-36420.
Authored-by: xiepengjie <xiepengjie@kuaishou.com>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>
8230a2a700