[TD-3177] <fix>: fix demo.c checking result error mistake.

.gitignore

@@ -27,7 +27,6 @@ tests/hdfs/
 nmake/
 sln/
 hdfs/
-c/
 taoshebei/
 taosdalipu/
 Target/

tests/examples/c/demo.c

@@ -92,15 +92,14 @@ void Test(TAOS *taos, char *qstr, int index)  {
     //   printf("insert row: %i, reason:%s\n", i, taos_errstr(taos));
     // }
     TAOS_RES *result1 = taos_query(taos, qstr);
-    if (result1) {
-      printf("insert row: %i\n", i);
-    } else {
-      printf("failed to insert row: %i, reason:%s\n", i, "null result"/*taos_errstr(result)*/);
+    if (result1 == NULL || taos_errno(result1) != 0) {
+      printf("failed to insert row, reason:%s\n", taos_errstr(result1));    
       taos_free_result(result1);
       exit(1);
+    } else {
+      printf("insert row: %i\n", i);
     }
     taos_free_result(result1);
-
   }
   printf("success to insert rows, total %d rows\n", i);