fix(asgi): fix KeyError if transaction does not exist

Author: kevinji

sentry_sdk/integrations/asgi.py

@@ -267,9 +267,11 @@ def event_processor(self, event, hint, asgi_scope):
         event["request"] = deepcopy(request_data)
 
         # Only set transaction name if not already set by Starlette or FastAPI (or other frameworks)
-        already_set = event["transaction"] != _DEFAULT_TRANSACTION_NAME and event[
-            "transaction_info"
-        ].get("source") in [
+        already_set = event.get(
+            "transaction"
+        ) != _DEFAULT_TRANSACTION_NAME and event.get("transaction_info", {}).get(
+            "source"
+        ) in [
             TransactionSource.COMPONENT,
             TransactionSource.ROUTE,
             TransactionSource.CUSTOM,