Merge branch 'master' into bot-api-8.1

Author: OvyFlash

configs.go

@@ -2179,9 +2179,11 @@ func (config InvoiceLinkConfig) params() (Params, error) {
 	params.AddNonZero("subscription_period", config.SubscriptionPeriod)
 	params.AddNonEmpty("provider_token", config.ProviderToken)
 	params.AddNonZero("max_tip_amount", config.MaxTipAmount)
-	err = params.AddInterface("suggested_tip_amounts", config.SuggestedTipAmounts)
-	if err != nil {
-		return params, err
+	if len(config.SuggestedTipAmounts) > 0 {
+		err := params.AddInterface("suggested_tip_amounts", config.SuggestedTipAmounts)
+		if err != nil {
+			return params, err
+		}
 	}
 	params.AddNonEmpty("provider_data", config.ProviderData)
 	params.AddNonEmpty("photo_url", config.PhotoURL)
@@ -2196,7 +2198,7 @@ func (config InvoiceLinkConfig) params() (Params, error) {
 	params.AddBool("send_email_to_provider", config.SendEmailToProvider)
 	params.AddBool("is_flexible", config.IsFlexible)
 
-	return params, err
+	return params, nil
 }
 
 func (config InvoiceLinkConfig) method() string {