fix test framework

tests/pytest/util/dnodes.py

@@ -112,7 +112,7 @@ class TDSimClient:
         
         # update extra client config
         clientCfgkeys = ["clientMerge"]
-        if updatecfgDict[0] and updatecfgDict[0][0]:
+        if bool(updatecfgDict) and updatecfgDict[0] and updatecfgDict[0][0]:
             for key, value in updatecfgDict[0][0].items():                
                 if key in clientCfgkeys:
                     self.cfg(key, value)