bgscan: Do not initialize bgscan if disabled by user

Do not initialize bgscan if the user explicitly set bgscan to an empty
string. Without this patch wpa_supplicant tries to initialize bgscan to
the first option if the string is empty.

Signed-off-by: David Spinadel <david.spinadel@intel.com>

wpa_supplicant/wpa_supplicant.c

@@ -573,7 +573,7 @@ static void wpa_supplicant_start_bgscan(struct wpa_supplicant *wpa_s)
 		name = wpa_s->current_ssid->bgscan;
 	else
 		name = wpa_s->conf->bgscan;
-	if (name == NULL)
+	if (name == NULL || name[0] == '\0')
 		return;
 	if (wpas_driver_bss_selection(wpa_s))
 		return;

wpa_supplicant/wpa_supplicant.conf

@@ -603,6 +603,8 @@ fast_reauth=1
 # bgscan="learn:<short bgscan interval in seconds>:<signal strength threshold>:
 # <long interval>[:<database file name>]"
 # bgscan="learn:30:-45:300:/etc/wpa_supplicant/network1.bgscan"
+# Explicitly disable bgscan by setting
+# bgscan=""
 #
 # This option can also be set outside of all network blocks for the bgscan
 # parameter to apply for all the networks that have no specific bgscan