Merge pull request #4461 from pjdarton/jenkins-54496

[JENKINS-54496] - Don't log node-monitoring errors from deleted nodes

core/src/main/java/hudson/node_monitors/AbstractAsyncNodeMonitorDescriptor.java

@@ -124,6 +124,11 @@ public abstract class AbstractAsyncNodeMonitorDescriptor<T> extends AbstractNode
     }
 
     private void error(Computer c, Throwable x) {
+        // JENKINS-54496: don't log if c was removed from Jenkins after we'd started monitoring
+        final boolean cIsStillCurrent = Jenkins.get().getComputer(c.getName()) == c;
+        if (!cIsStillCurrent) {
+            return;
+        }
         if (c instanceof SlaveComputer) {
             Functions.printStackTrace(x, ((SlaveComputer) c).getListener().error("Failed to monitor for " + getDisplayName()));
         } else {