Prevent crash

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

@@ -1874,11 +1874,13 @@ public class FragmentMessages extends FragmentBase implements SharedPreferences.
                                     message.account, message.thread, threading ? null : id, message.folder);
                             for (EntityMessage threaded : messages) {
                                 EntityFolder target = db.folder().getFolderByType(message.account, type);
+                                if (target != null) {
                                     EntityAccount account = db.account().getAccount(target.account);
                                     result.add(new MessageTarget(threaded, account, target));
                                 }
                             }
                         }
+                    }
 
                     db.setTransactionSuccessful();
                 } finally {