Do not fail stack trace query on a closed workflow

temporal-sdk/src/main/java/io/temporal/internal/sync/DeterministicRunnerImpl.java

@@ -415,7 +415,9 @@ public String stackTrace() {
     StringBuilder result = new StringBuilder();
     lock.lock();
     try {
-      checkClosed();
+      if (closed) {
+        return "Workflow is closed.";
+      }
       for (WorkflowThread coroutine : threads) {
         if (result.length() > 0) {
           result.append("\n");

temporal-sdk/src/test/java/io/temporal/workflow/SyncTest.java

@@ -91,6 +91,8 @@ public void testSyncUntypedAndStackTrace() {
     assertTrue(stackTrace, stackTrace.contains("activityWithDelay"));
     String result = workflowStub.getResult(String.class);
     assertEquals("activity10", result);
+    // No stacktrace after the workflow is closed. Assert message.
+    assertEquals("Workflow is closed.", workflowStub.query(QUERY_TYPE_STACK_TRACE, String.class));
   }
 
   @Test