fix: drop redundant None-guard on agent_result in agent:end payload

agent_result is guaranteed non-None at this point — line 17926 calls
.get() on it unconditionally, and line 18099 in the same block does
the same without the guard. The if/else was dead defensive code
inconsistent with surrounding access patterns.

gateway/run.py

@@ -18112,8 +18112,8 @@ class GatewayRunner(GatewayAuthorizationMixin, GatewayKanbanWatchersMixin, Gatew
             await self.hooks.emit("agent:end", {
                 **hook_ctx,
                 "response": (response or "")[:500],
-                "model": agent_result.get("model", "") if agent_result else "",
-                "provider": agent_result.get("provider", "") if agent_result else "",
+                "model": agent_result.get("model", ""),
+                "provider": agent_result.get("provider", ""),
             })
             
             # Check for pending process watchers (check_interval on background processes)