Editing or viewing a contribution from "View Participant" leads to fatal error

To recreate

• view a participant record that has an associated contribution record
• click view or edit on the contribution record actions (lower part of "View Participant" page)
• click Save or Cancel (if edit) or Done (if view contrib).

We're not retaining the participant id in this condition so Save or Cancel from Edit Contribution and Done from View Contribution winds up throwing a fatal error because it tries to go back to view/participant page but the id param is empty - you get to this URL:

civicrm/contact/view/participant?reset=1&action=update&id=&cid=102&context=participant&selectedChild=event

and get fatal error with this backtrace
/Users/dgg/svn/crm_v3.2/CRM/Core/Error.php, backtrace, 254
/Users/dgg/svn/crm_v3.2/CRM/Core/DAO.php, fatal, 708
/Users/dgg/svn/crm_v3.2/CRM/Event/Form/Participant.php, getFieldValue, 491
/Users/dgg/svn/crm_v3.2/CRM/Core/Form.php, setDefaultValues, 328
/Users/dgg/svn/crm_v3.2/CRM/Core/QuickForm/Action/Display.php, buildForm, 99
/Users/dgg/svn/crm_v3.2/packages/HTML/QuickForm/Controller.php, perform, 203
/Users/dgg/svn/crm_v3.2/packages/HTML/QuickForm/Page.php, handle, 103
/Users/dgg/svn/crm_v3.2/CRM/Core/Controller.php, handle, 279
/Users/dgg/svn/crm_v3.2/CRM/Event/Page/Tab.php, run, 113
/Users/dgg/svn/crm_v3.2/CRM/Event/Page/Tab.php, edit, 174
/Users/dgg/svn/crm_v3.2/CRM/Core/Invoke.php, run, 219
/Users/dgg/svn/crm_v3.2/drupal/civicrm.module, invoke, 350
, civicrm_invoke,
/Users/dgg/htdocs/d6/includes/menu.inc, call_user_func_array, 348
/Users/dgg/htdocs/d6/index.php, menu_execute_active_handler, 18