Disable delete for read-only folders

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

@@ -2985,6 +2985,7 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
             popupMenu.getMenu().findItem(R.id.menu_copy).setEnabled(message.uid != null && !message.folderReadOnly);
             popupMenu.getMenu().findItem(R.id.menu_copy).setVisible(message.accountProtocol == EntityAccount.TYPE_IMAP);
 
+            popupMenu.getMenu().findItem(R.id.menu_delete).setEnabled(message.uid == null || !message.folderReadOnly);
             popupMenu.getMenu().findItem(R.id.menu_delete).setVisible(message.accountProtocol == EntityAccount.TYPE_IMAP);
 
             popupMenu.getMenu().findItem(R.id.menu_resync).setEnabled(message.uid != null);