Fix comment reflection

Author: xzkostyan

clickhouse_sqlalchemy/drivers/base.py

@@ -432,6 +432,9 @@ def get_table_comment(self, connection, table_name, schema=None, **kw):
         if not self.supports_table_comment_reflection:
             raise NotImplementedError()
 
+        if not self.engine_reflection:
+            return {}
+
         database = schema if schema else connection.engine.url.database
 
         query = text(