Deferences avatar task on destroy

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

@@ -1534,6 +1534,11 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
                         bindContactInfo(amessage, info, addresses);
                     }
 
+                    @Override
+                    protected void onDestroyed(Bundle args) {
+                        taskContactInfo = null;
+                    }
+
                     @Override
                     protected void onException(Bundle args, Throwable ex) {
                         Log.unexpectedError(parentFragment.getParentFragmentManager(), ex);