Don't treat sends to a group with unregistered users as an error

js/background.js

@@ -1109,9 +1109,10 @@
       conversationId: data.destination,
       type: 'outgoing',
       sent: true,
-      expirationStartTimestamp: data.expirationStartTimestamp
-        ? Math.min(data.expirationStartTimestamp, Date.now())
-        : null,
+      expirationStartTimestamp: Math.min(
+        data.expirationStartTimestamp || data.timestamp || Date.now(),
+        Date.now()
+      ),
     });
   }
 

js/models/messages.js

@@ -879,17 +879,33 @@
               promises.push(c.getProfiles());
             }
           } else {
-            this.saveErrors(result.errors);
             if (result.successfulNumbers.length > 0) {
               const sentTo = this.get('sent_to') || [];
 
-              // Note: In a partially-successful group send, we do not start
-              //   the expiration timer.
+              // In groups, we don't treat unregistered users as a user-visible
+              //   error. The message will look successful, but the details
+              //   screen will show that we didn't send to these unregistered users.
+              const filteredErrors = _.reject(
+                result.errors,
+                error => error.name === 'UnregisteredUserError'
+              );
+
+              // We don't start the expiration timer if there are real errors
+              //   left after filtering out all of the unregistered user errors.
+              const expirationStartTimestamp = filteredErrors.length
+                ? null
+                : Date.now();
+
+              this.saveErrors(filteredErrors);
+
               this.set({
                 sent_to: _.union(sentTo, result.successfulNumbers),
                 sent: true,
+                expirationStartTimestamp,
               });
               promises.push(this.sendSyncMessage());
+            } else {
+              this.saveErrors(result.errors);
             }
             promises = promises.concat(
               _.map(result.errors, error => {