Skip reporting IAB canceled

app/src/main/java/eu/faircode/email/ActivityBilling.java

@@ -515,6 +515,7 @@ public class ActivityBilling extends ActivityBase implements PurchasesUpdatedLis
 
         EntityLog.log(this, message);
 
+        if (result.getResponseCode() != BillingClient.BillingResponseCode.USER_CANCELED)
             for (IBillingListener listener : listeners)
                 listener.onError(message);
     }