fix 部分api请求失败情况下，不会噶了

pywxdump/db/dbMicro.py

@@ -59,7 +59,7 @@ class MicroHandler(DatabaseBase):
         :param id_is_key: id_is_key: True: id作为key，False: name作为key
         :return:
         """
-        if (self.table_exist.get("ContactLabel") is None) or (not self.table_exist.get("ContactLabel")):
+        if not self.table_exist.get("ContactLabel", False):
             return []
         sql = "SELECT LabelId, LabelName FROM ContactLabel ORDER BY LabelName ASC;"
         result = self.execute(sql)