fix: fix login logic

app.py

@@ -31,10 +31,12 @@ def check_login(username, password):
         conn.close()
         if result and result[0] == "admin":
             return "admin"
-        return "user"
+        elif result and result[0] == "user":
+            return "user"
+        return None  # Return None for failed login
     except:
         conn.close()
-        return "user"
+        return None  # Return None for any errors
 
 
 def respond(
@@ -144,7 +146,11 @@ def create_interface():
 
         def attempt_login(username, password):
             user_role = check_login(username, password)
-            role.value = user_role  # Update the role state
+            if user_role is None:
+                return {
+                    login_status: "Login failed! Invalid credentials.",
+                }
+            role.value = user_role
             return {
                 login_block: gr.Group(visible=False),
                 chat_block: gr.Group(visible=True),