perf: validate config_path before checking existence (#6722)

Add a check for empty config_path in check_exist method

Author: LIghtJUNction

astrbot/core/config/astrbot_config.py

@@ -178,4 +178,6 @@ def __setattr__(self, key, value) -> None:
         self[key] = value
 
     def check_exist(self) -> bool:
+        if not self.config_path:  # 加判空
+            return False
         return os.path.exists(self.config_path)