Don't issue errors when group members unregister

Fixes #2408
Fixes #4550
Closes #5318

// FREEBIE

src/org/thoughtcrime/securesms/jobs/PushGroupSendJob.java

@@ -104,12 +104,18 @@ public class PushGroupSendJob extends PushSendJob implements InjectableType {
       }
 
       database.addFailures(messageId, failures);
-      database.markAsSentFailed(messageId);
       database.markAsPush(messageId);
 
+      if (e.getNetworkExceptions().isEmpty() && e.getUntrustedIdentityExceptions().isEmpty()) {
+        database.markAsSecure(messageId);
+        database.markAsSent(messageId);
+        markAttachmentsUploaded(messageId, message.getAttachments());
+      } else {
+        database.markAsSentFailed(messageId);
         notifyMediaMessageDeliveryFailed(context, messageId);
       }
     }
+  }
 
   @Override
   public boolean onShouldRetryThrowable(Exception exception) {