fix(client): set the initial value for num_of_rows.

source/client/src/clientJniConnector.c

@@ -581,8 +581,8 @@ JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_fetchBlockImp(JNI
     return JNI_RESULT_SET_NULL;
   }
 
-  void   *data;
-  int32_t numOfRows;
+  void   *data = NULL;
+  int32_t numOfRows = 0;
   int     error_code = taos_fetch_raw_block(tres, &numOfRows, &data);
   if (numOfRows == 0) {
     if (error_code == JNI_SUCCESS) {

source/client/src/clientMain.c

@@ -611,6 +611,9 @@ int taos_fetch_block_s(TAOS_RES *res, int *numOfRows, TAOS_ROW *rows) {
 }
 
 int taos_fetch_raw_block(TAOS_RES *res, int *numOfRows, void **pData) {
+  *numOfRows = 0;
+  *pData = NULL;
+
   if (res == NULL || TD_RES_TMQ_META(res)) {
     return 0;
   }

source/client/src/clientTmqConnector.c

@@ -361,8 +361,8 @@ JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_tmq_TMQConnector_fetchRawBlockImp(
 
   TAOS_RES *tres = (TAOS_RES *)res;
 
-  void   *data;
-  int32_t numOfRows;
+  void   *data = NULL;
+  int32_t numOfRows = 0;
   int     error_code = taos_fetch_raw_block(tres, &numOfRows, &data);
   if (numOfRows == 0) {
     if (error_code == JNI_SUCCESS) {