Added fail-safe

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

@@ -3374,6 +3374,9 @@ public class FragmentMessages extends FragmentBase
 
                 @Override
                 protected void onExecuted(Bundle args, ArrayList<MessageTarget> result) {
+                    if (result == null || result.size() == 0)
+                        redraw(NO_POSITION);
+                    else
                         moveUndo(result);
                 }