fix crash

source/libs/function/src/builtins.c

@@ -1579,6 +1579,7 @@ static int32_t translateTimeDiff(SFunctionNode* pFunc, char* pErrBuf, int32_t le
   //add database precision as param
   uint8_t dbPrec = pFunc->node.resType.precision;
 
+  if (3 == numOfParams) {
     int32_t ret = validateTimeUnitParam(dbPrec, (SValueNode *)nodesListGetNode(pFunc->pParameterList, 2));
     if (ret == TIME_UNIT_TOO_SMALL) {
       return buildFuncErrMsg(pErrBuf, len, TSDB_CODE_FUNC_FUNTION_ERROR,
@@ -1587,6 +1588,7 @@ static int32_t translateTimeDiff(SFunctionNode* pFunc, char* pErrBuf, int32_t le
       return buildFuncErrMsg(pErrBuf, len, TSDB_CODE_FUNC_FUNTION_ERROR,
                              "TIMEDIFF function time unit parameter should be one of the following: [1u, 1a, 1s, 1m, 1h, 1d, 1w]");
     }
+  }
 
   addDbPrecisonParam(&pFunc->pParameterList, dbPrec);