chore(internal): Resolve processing error on sentry events (#95376)

Resolves a common processing error on most internal errors

<img width="496" height="97" alt="image"
src="https://github.com/user-attachments/assets/85fc34c5-81cd-4ae9-9c7d-782c78172c87"
/>

Author: leeandher

src/sentry/api/base.py

@@ -377,7 +377,8 @@ def dispatch(self, request: Request, *args, **kwargs) -> Response:
             self.request = request
             self.headers = self.default_response_headers  # deprecate?
 
-        sentry_sdk.set_tag("http.referer", request.META.get("HTTP_REFERER", ""))
+        if request.META.get("HTTP_REFERER"):
+            sentry_sdk.set_tag("http.referer", request.META.get("HTTP_REFERER"))
 
         start_time = time.time()