app/testpmd: avoid potential outside of array reference

The order of comparison is wrong, and potentially allows
referencing past the array.

Link: https://pvs-studio.com/en/blog/posts/cpp/1179/
Fixes: 3e3edab ("ethdev: add flow quota")
Cc: stable@dpdk.org

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Chengwen Feng <fengchengwen@huawei.com>

app/test-pmd/cmdline_flow.c

@@ -12892,7 +12892,7 @@ comp_names_to_index(struct context *ctx, const struct token *token,
 	RTE_SET_USED(token);
 	if (!buf)
 		return names_size;
-	if (names[ent] && ent < names_size)
+	if (ent < names_size && names[ent] != NULL)
 		return rte_strscpy(buf, names[ent], size);
 	return -1;