omit a paynym contact whose payment code does not parse rather than keeping it with a null code or failing the whole paynym response

### drongo
@@ -1 +1 @@
-Subproject commit eb3cf3e577265165875b70de60d5333f827e279e
+Subproject commit 9a8c659b49b6cb3010855b74a37e66e076521490

### src/main/java/com/sparrowwallet/sparrow/paynym/PayNym.java
@@ -9,6 +9,7 @@
 
 import java.util.Collections;
 import java.util.List;
+import java.util.Optional;
 
 import static com.sparrowwallet.drongo.bip47.PaymentCode.SEGWIT_SCRIPT_TYPES;
 import static com.sparrowwallet.drongo.bip47.PaymentCode.V1_SCRIPT_TYPES;
@@ -70,16 +71,13 @@ public static List<ScriptType> getV1ScriptTypes() {
         return V1_SCRIPT_TYPES;
     }
 
-    public static PayNym fromString(String strPaymentCode, String nymId, String nymName, boolean segwit, List<PayNym> following, List<PayNym> followers) {
-        PaymentCode paymentCode;
+    public static Optional<PayNym> fromString(String strPaymentCode, String nymId, String nymName, boolean segwit, List<PayNym> following, List<PayNym> followers) {
         try {
-            paymentCode = new PaymentCode(strPaymentCode);
+            return Optional.of(new PayNym(new PaymentCode(strPaymentCode), nymId, nymName, segwit, following, followers));
         } catch(InvalidPaymentCodeException e) {
             log.error("Error creating PayNym from payment code " + strPaymentCode, e);
-            paymentCode = null;
+            return Optional.empty();
         }
-
-        return new PayNym(paymentCode, nymId, nymName, segwit, following, followers);
     }
 
     public static PayNym fromWallet(Wallet bip47Wallet) {

### src/main/java/com/sparrowwallet/sparrow/paynym/PayNymService.java
@@ -206,13 +206,14 @@ public static Observable<PayNym> getPayNym(String nymIdentifier, boolean compact
             }
 
             List<Map<String, Object>> followingMaps = (List<Map<String, Object>>)nymMap.get("following");
-            List<PayNym> following = followingMaps.stream().map(followingMap -> {
-                return PayNym.fromString((String)followingMap.get("code"), (String)followingMap.get("nymId"), (String)followingMap.get("nymName"), (Boolean)followingMap.get("segwit"), Collections.emptyList(), Collections.emptyList());
+            //An entry whose payment code does not parse is omitted rather than failing the whole PayNym
+            List<PayNym> following = followingMaps.stream().flatMap(followingMap -> {
+                return PayNym.fromString((String)followingMap.get("code"), (String)followingMap.get("nymId"), (String)followingMap.get("nymName"), (Boolean)followingMap.get("segwit"), Collections.emptyList(), Collections.emptyList()).stream();
             }).collect(Collectors.toList());
 
             List<Map<String, Object>> followersMaps = (List<Map<String, Object>>)nymMap.get("followers");
-            List<PayNym> followers = followersMaps.stream().map(followerMap -> {
-                return PayNym.fromString((String)followerMap.get("code"), (String)followerMap.get("nymId"), (String)followerMap.get("nymName"), (Boolean)followerMap.get("segwit"), Collections.emptyList(), Collections.emptyList());
+            List<PayNym> followers = followersMaps.stream().flatMap(followerMap -> {
+                return PayNym.fromString((String)followerMap.get("code"), (String)followerMap.get("nymId"), (String)followerMap.get("nymName"), (Boolean)followerMap.get("segwit"), Collections.emptyList(), Collections.emptyList()).stream();
             }).collect(Collectors.toList());
 
             return new PayNym(code, (String)nymMap.get("nymID"), (String)nymMap.get("nymName"), (Boolean)nymMap.get("segwit"), following, followers);

### src/test/java/com/sparrowwallet/sparrow/paynym/PayNymTest.java
@@ -0,0 +1,33 @@
+package com.sparrowwallet.sparrow.paynym;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Collections;
+import java.util.Optional;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * A contact entry in a PayNym response whose payment code does not parse is omitted, rather than becoming a PayNym with no payment code that the contact
+ * lists and search then dereference.
+ */
+public class PayNymTest {
+    private static final String PAYMENT_CODE = "PM8TJTLJbPRGxSbc8EJi42Wrr6QbNSaSSVJ5Y3E4pbCYiTHUskHg13935Ubb7q8tx9GVbh2UuRnBc3WSyJHhUrw8KhprKnn9eDznYGieTzFcwQRya4GA";
+
+    @Test
+    public void parsesAValidPaymentCode() {
+        Optional<PayNym> payNym = PayNym.fromString(PAYMENT_CODE, "id", "+name", true, Collections.emptyList(), Collections.emptyList());
+        assertTrue(payNym.isPresent());
+        assertEquals(PAYMENT_CODE, payNym.get().paymentCode().toString());
+    }
+
+    @Test
+    public void omitsAnUnparseablePaymentCode() {
+        assertTrue(PayNym.fromString("not-a-payment-code", "id", "+name", true, Collections.emptyList(), Collections.emptyList()).isEmpty());
+
+        //Valid Base58 with a corrupted checksum
+        String corrupted = PAYMENT_CODE.substring(0, PAYMENT_CODE.length() - 1) + (PAYMENT_CODE.endsWith("A") ? "B" : "A");
+        assertTrue(PayNym.fromString(corrupted, "id", "+name", true, Collections.emptyList(), Collections.emptyList()).isEmpty());
+    }
+}