Update app.py

app.py

@@ -1143,7 +1143,7 @@ DARK_MODE = False
 def login_student(username: str, password: str) -> tuple:
     global CURRENT_USER, DARK_MODE
     student_data = student_service.authenticate_student(username, password)
-    if student_
+    if student_:
         CURRENT_USER = username
         DARK_MODE = student_data["dark_mode"]
         chat_history = student_service.get_chat_history(username)