prevent prelim in case of any advocate action; fixes #253
The second preliminary alert should not go out in case the superevent has already been vetted i.e., the ADVNO
label is present on the superevent. This is also true in case of ADVOK
which means that the initial alert has already gone. This can happen if the ADVOK
button is pressed before the second preliminary is launched and would prevent a preliminary to go after an initial is sent
When revising the superevent to send the preliminary alert, also update the preferred event.
Edited by Deep Chatterjee