add null json value support

src/client/src/tscUtil.c

@@ -777,7 +777,6 @@ static void setResRawPtrImpl(SSqlRes* pRes, SInternalField* pInfo, int32_t i, bo
               tscError("charset:%s to %s. val:%s convert failed.", DEFAULT_UNICODE_ENCODEC, tsCharset, (char*)p);
             }
           }
-          return;
         }else if (type == TSDB_DATA_TYPE_DOUBLE) {
           double jsonVd = *(double*)(realData);
           sprintf(varDataVal(dst), "%.9lf", jsonVd);

src/query/src/qExecutor.c

@@ -3401,7 +3401,7 @@ static void doSetTagValueInParam(void* pTable, char* param, int32_t paramLen, in
     }else{
       getJsonTagValueAll(val, jsonVal, TSDB_MAX_JSON_TAGS_LEN);
     }
-    tVariantCreateFromBinary(tag, jsonVal, varDataTLen(jsonVal), type);
+    tVariantCreateFromBinary(tag, jsonVal, CHAR_BYTES + varDataTLen(POINTER_SHIFT(jsonVal,CHAR_BYTES)), type);
   } else {
     tVariantCreateFromBinary(tag, val, bytes, type);
   }