Issue:

If you reduce the number of executors to 0 on a dedicated agent and hit save it will throw a 404 not found error. Then that node page is removed from the UI but still exists on the $JENKINS_HOME/nodes folder.

Steps to Reproduce:

1. Create a dedicated node(the type does not matter) with at least 1 executor
2. Save that node
3. Configure that node again and drop executors from 1 to 0
4. Save the configuration
5. Watch the 404 error happen

Expected results:
I would either expect a error thrown before saving or for the node to still exist but the worst is that it disappears off the UI and the only way to get it back is to adjust the filesystem and restart

I attached screen shots and the config.xml after the save