fix layout twitching

[mjbogusz]

This change fixes the minor layout/visualizer twitching.

I've noticed the twitching on all but the first visualizer, Ubuntu 20.04, Firefox.
I'll add screen captures showing before/after soon.

[mjbogusz]

Before (notice the visualizer on the right jumping slightly up and down):

After:

The data was just a statically published int:

ros2 topic pub --rate 100 --print 100 /test1 std_msgs/msg/Int32 "{data: 10}"

[dheera]

Thank you! I'll test shortly.