Small fix

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

@@ -4284,6 +4284,8 @@ class Core {
                                         istore, ifolder, (MimeMessage) isub[j],
                                         false, download && initialize == 0,
                                         rules, state, stats);
+                                if (message == null)
+                                    modseq = null;
                                 ids[from + j] = (message == null || message.ui_hide ? null : message.id);
                             } catch (MessageRemovedException ex) {
                                 Log.w(folder.name, ex);