Add double-end guard to NoOpStreamedSpan

Co-Authored-By: gpt-5.3-codex-high <noreply@anthropic.com>

Author: cursoragent

sentry_sdk/traces.py

@@ -448,7 +448,7 @@ def _start(self) -> None:
         self._previous_span_on_scope = old_span
 
     def _end(self, end_timestamp: "Optional[Union[float, datetime]]" = None) -> None:
-        if self._scope is None:
+        if self._scope is None or not hasattr(self, "_previous_span_on_scope"):
             return
 
         with capture_internal_exceptions():