nl80211: Avoid wpa_printf %s call with NULL pointer in set_param()

While most C libraries print "(null)" when NULL is used as an argument
to printf format string %s, this is not really necessary to print here,
so move the debug print to be after the NULL check.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>

src/drivers/driver_nl80211.c

@@ -6691,9 +6691,9 @@ static int nl80211_send_frame(void *priv, const u8 *data, size_t data_len,
 
 static int nl80211_set_param(void *priv, const char *param)
 {
-	wpa_printf(MSG_DEBUG, "nl80211: driver param='%s'", param);
 	if (param == NULL)
 		return 0;
+	wpa_printf(MSG_DEBUG, "nl80211: driver param='%s'", param);
 
 #ifdef CONFIG_P2P
 	if (os_strstr(param, "use_p2p_group_interface=1")) {