Ignore pool error when worker is already not the part of the pool.

PiperOrigin-RevId: 401751715
diff --git a/src/main/java/com/google/devtools/build/lib/worker/WorkerSpawnRunner.java b/src/main/java/com/google/devtools/build/lib/worker/WorkerSpawnRunner.java
index 489df91..61a8b0f 100644
--- a/src/main/java/com/google/devtools/build/lib/worker/WorkerSpawnRunner.java
+++ b/src/main/java/com/google/devtools/build/lib/worker/WorkerSpawnRunner.java
@@ -542,7 +542,11 @@
                 }
               } finally {
                 if (w != null) {
-                  workers.returnObject(key, w);
+                  try {
+                    workers.returnObject(key, w);
+                  } catch (IllegalStateException e3) {
+                    // The worker already not part of the pool
+                  }
                 }
               }
             },