feat: initialize browser and close it to resolve UnboundLocalError.

Author: MeshkatShB

webui.py

@@ -199,6 +199,7 @@ async def run_custom_agent(
     controller = CustomController()
     playwright = None
     browser_context_ = None
+    browser = None  # Initialize browser to None
     try:
         if use_own_browser:
             playwright = await async_playwright().start()
@@ -278,14 +279,18 @@ async def run_custom_agent(
         model_actions = ""
         model_thoughts = ""
     finally:
-        # 显式关闭持久化上下文
+        # Close persistent context if it was initialized
         if browser_context_:
             await browser_context_.close()
 
-        # 关闭 Playwright 对象
+        # Stop Playwright if it was started
         if playwright:
             await playwright.stop()
-        await browser.close()
+
+        # Close the browser if it was initialized
+        if browser:
+            await browser.close()
+
     return final_result, errors, model_actions, model_thoughts
 
 # Define the theme map globally