Update sentry_sdk/integrations/celery/__init__.py

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: sentrivana

sentry_sdk/integrations/celery/__init__.py

@@ -233,9 +233,12 @@ def _update_celery_task_headers(
 
             # Preserve user-provided custom headers in the inner "headers" dict
             # so they survive to task.request.headers on the worker (celery#4875).
-            for key, value in original_headers.items():
-                if key != "headers" and key not in updated_headers["headers"]:
-                    updated_headers["headers"][key] = value
+        # Preserve user-provided custom headers in the inner "headers" dict
+        # so they survive to task.request.headers on the worker (celery#4875).
+        inner_headers = updated_headers.setdefault("headers", {})
+        for key, value in original_headers.items():
+            if key != "headers" and key not in inner_headers:
+                inner_headers[key] = value
 
     return updated_headers