Fix a panic in the assistant panel (#8244)

Release Notes:

- Fixed a panic in the assistant panel when the app is shutting down.

crates/assistant/src/assistant_panel.rs

@@ -122,16 +122,13 @@ impl AssistantPanel {
                 .await
                 .log_err()
                 .unwrap_or_default();
-            let (api_url, model_name) = cx
-                .update(|cx| {
-                    let settings = AssistantSettings::get_global(cx);
-                    (
-                        settings.openai_api_url.clone(),
-                        settings.default_open_ai_model.full_name().to_string(),
-                    )
-                })
-                .log_err()
-                .unwrap();
+            let (api_url, model_name) = cx.update(|cx| {
+                let settings = AssistantSettings::get_global(cx);
+                (
+                    settings.openai_api_url.clone(),
+                    settings.default_open_ai_model.full_name().to_string(),
+                )
+            })?;
             let completion_provider = OpenAiCompletionProvider::new(
                 api_url,
                 model_name,