hotfix(custom): allow empty servers data

internal/configuration/settings/serverselection.go

@@ -141,7 +141,7 @@ func getLocationFilterChoices(vpnServiceProvider string, ss *ServerSelection,
 	ispChoices, nameChoices, hostnameChoices []string,
 	err error) {
 	providerServers, ok := allServers.ProviderToServers[vpnServiceProvider]
-	if !ok {
+	if !ok && vpnServiceProvider != providers.Custom {
 		panic(fmt.Sprintf("VPN service provider unknown: %s", vpnServiceProvider))
 	}
 	servers := providerServers.Servers

internal/models/servers.go

@@ -16,6 +16,10 @@ type AllServers struct {
 }
 
 func (a *AllServers) ServersSlice(provider string) []Server {
+	if provider == providers.Custom {
+		return nil
+	}
+
 	servers, ok := a.ProviderToServers[provider]
 	if !ok {
 		panic(fmt.Sprintf("provider %s not found in all servers", provider))