hotfix(updater): do not default to custom

Dockerfile

@@ -162,6 +162,7 @@ ENV VPNSP=pia \
     SHADOWSOCKS_CIPHER=chacha20-ietf-poly1305 \
     # Server data updater
     UPDATER_PERIOD=0 \
+    UPDATER_VPN_SERVICE_PROVIDERS= \
     # Public IP
     PUBLICIP_FILE="/tmp/gluetun/ip" \
     PUBLICIP_PERIOD=12h \

internal/configuration/settings/updater.go

@@ -93,7 +93,7 @@ func (u *Updater) SetDefaults(vpnProvider string) {
 	u.Period = helpers.DefaultDuration(u.Period, 0)
 	u.DNSAddress = helpers.DefaultIP(u.DNSAddress, net.IPv4(1, 1, 1, 1))
 	u.CLI = helpers.DefaultBool(u.CLI, false)
-	if len(u.Providers) == 0 {
+	if len(u.Providers) == 0 && vpnProvider != constants.Custom {
 		u.Providers = []string{vpnProvider}
 	}
 }