fix case

tests/system-test/2-query/union.py

@@ -99,7 +99,7 @@ class TDTestCase:
         return join_condition
 
     def __where_condition(self, col=None, tbname=None, query_conditon=None):
-        if query_conditon:
+        if query_conditon and isinstance(query_conditon, str):
             if query_conditon.startswith("count"):
                 query_conditon = query_conditon[6:-1]
             elif query_conditon.startswith("max"):
@@ -125,6 +125,7 @@ class TDTestCase:
 
 
     def __group_condition(self, col, having = None):
+        if isinstance(col, str):
             if col.startswith("count"):
                 col = col[6:-1]
             elif col.startswith("max"):