fix: skip random challenge when no bot is found (#1210)

Return immediately when matchmaking cannot pick an opponent, avoiding the misleading 'Will challenge None' log line.

Validation: python3 -m py_compile lichess-bot/lib/matchmaking.py

Author: ilAYAli

lib/matchmaking.py

@@ -237,8 +237,14 @@ def challenge(self, active_games: set[str], challenge_queue: MULTIPROCESSING_LIS
         logger.info("Challenging a random bot")
         self.update_user_profile()
         bot_username, base_time, increment, days, variant, mode = self.choose_opponent()
+        if not bot_username:
+            logger.info("No challenge will be created.")
+            self.challenge_id = ""
+            self.rate_limit_timer = Timer(seconds(60))
+            return
+
         logger.info(f"Will challenge {bot_username} for a {variant} game.")
-        challenge_id = self.create_challenge(bot_username, base_time, increment, days, variant, mode) if bot_username else ""
+        challenge_id = self.create_challenge(bot_username, base_time, increment, days, variant, mode)
         logger.info(f"Challenge id is {challenge_id or 'None'}.")
         self.challenge_id = challenge_id