Trying to edit contact with multiple subtypes gives error: Invalid Filter

Summary

Trying to access the main contact edit form for a contact that has multiple contact subtypes gives fatal error: Invalid Filter.

Replicated on 4.6 & 4.7 demo:

http://d46.demo.civicrm.org/civicrm/contact/view?reset=1&cid=132
http://dmaster.demo.civicrm.org/civicrm/contact/view?reset=1&cid=155

Steps to replicate

1. Assign two contact subtypes to a contact: e.g. Student, Volunteer.
2. On contact summary, click Edit to open main contact edit form.

Expected behaviour:
Main contact edit form opens.

Actual behaviour:
Fatal error:
Sorry but we are not able to provide this at the moment.
Invalid Filter

Diagnosis

Appears related to other subtype issues in 4.6.16/4.7.7 . Debugging shows that CRM/Core/BAO/CustomGroup::validateSubTypeByEntity() is passed $subType 'Student,Volunteer', comma-separated. validateSubTypeByEntity() isn't set up to deal with a comma-separated list; instead it looks for 'Student,Volunteer' in the array $subTypes that it gets from a Contact getoptions API call. Of course it doesn't find 'Student,Volunteer' so it throws exception 'Invalid Filter'.

Backtrace:
#0 .../civicrm/CRM/Core/BAO/CustomGroup.php(653): CRM_Core_Error::backtrace()
#1 .../civicrm/CRM/Core/BAO/CustomGroup.php(438): CRM_Core_BAO_CustomGroup::validateSubTypeByEntity("Individual", "Student,Volunteer")
#2 .../civicrm/CRM/Custom/Form/CustomData.php(136): CRM_Core_BAO_CustomGroup::getTree("Individual", Object(CRM_Contact_Form_Contact), "132", NULL, "Student,Volunteer", NULL, TRUE, NULL)
#3 .../civicrm/CRM/Contact/Form/Contact.php(386): CRM_Custom_Form_CustomData::preProcess(Object(CRM_Contact_Form_Contact), NULL, "
Student
Volunteer
", 1, "Individual", "132")
#4 .../civicrm/CRM/Core/Form.php(455): CRM_Contact_Form_Contact->preProcess()
#5 .../civicrm/CRM/Core/QuickForm/Action/Display.php(94): CRM_Core_Form->buildForm()
#6 .../civicrm/packages/HTML/QuickForm/Controller.php(203): CRM_Core_QuickForm_Action_Display->perform(Object(CRM_Contact_Form_Contact), "display")
#7 .../civicrm/packages/HTML/QuickForm/Page.php(103): HTML_QuickForm_Controller->handle(Object(CRM_Contact_Form_Contact), "display")
#8 .../civicrm/CRM/Core/Controller.php(353): HTML_QuickForm_Page->handle("display")
#9 .../civicrm/CRM/Utils/Wrapper.php(115): CRM_Core_Controller->run()
#10 .../civicrm/CRM/Core/Invoke.php(286): CRM_Utils_Wrapper->run("CRM_Contact_Form_Contact", "New Contact", (Array:1))
#11 .../civicrm/CRM/Core/Invoke.php(86): CRM_Core_Invoke::runItem((Array:13))
#12 .../civicrm/CRM/Core/Invoke.php(54): CRM_Core_Invoke::_invoke((Array:3))
#13 .../civicrm/drupal/civicrm.module(489): CRM_Core_Invoke::invoke((Array:3))
#14 [internal function](): civicrm_invoke("contact", "add")
#15 /Users/davej/src/buildkit/build/d46/includes/menu.inc(527): call_user_func_array("civicrm_invoke", (Array:2))
#16 /Users/davej/src/buildkit/build/d46/index.php(21): menu_execute_active_handler()
#17