Expected one ParticipantPayment but found 0

Question

Civicrm Version 5.4.0

On New Participant Registration, I get an error "Expected one ParticipantPayment but found 0" when I try to register for an event which is not a paid event.

CiviCRM_API3_Exception: "Expected one ParticipantPayment but found 0"

 #0 C:\sites\default\files\civicrm\ext\org.civicrm.multidomaininvoicing\multidomaininvoicing.php(316):
 civicrm_api3("ParticipantPayment", "getvalue", (Array:4))
 #1 C:\sites\all\modules\civicrm\CRM\Utils\Hook.php(274): multidomaininvoicing_civicrm_postProcess("CRM_Event_Form_Participant",
 Object(CRM_Event_Form_Participant))
 #2 C:\sites\all\modules\civicrm\CRM\Utils\Hook\DrupalBase.php(84): CRM_Utils_Hook->runHooks((Array:69), "civicrm_postProcess", 2,
 "CRM_Event_Form_Participant", Object(CRM_Event_Form_Participant),
 NULL, NULL, NULL, NULL)
 #3 C:\sites\all\modules\civicrm\Civi\Core\CiviEventDispatcher.php(90): CRM_Utils_Hook_DrupalBase->invokeViaUF(2,
 "CRM_Event_Form_Participant", Object(CRM_Event_Form_Participant),
 NULL, NULL, NULL, NULL, "civicrm_postProcess")
 #4 [internal function](): Civi\Core\CiviEventDispatcher::delegateToUF(Object(Civi\Core\Event\GenericHookEvent),
 "hook_civicrm_postProcess", Object(Civi\Core\CiviEventDispatcher))
 #5 C:\sites\all\modules\civicrm\vendor\symfony\event-dispatcher\Symfony\Component\EventDispatcher\EventDispatcher.php(164):
 call_user_func((Array:2), Object(Civi\Core\Event\GenericHookEvent),
 "hook_civicrm_postProcess", Object(Civi\Core\CiviEventDispatcher))
 #6 C:\sites\all\modules\civicrm\vendor\symfony\event-dispatcher\Symfony\Component\EventDispatcher\EventDispatcher.php(53): Symfony\Component\EventDispatcher\EventDispatcher->doDispatch((Array:1),
 "hook_civicrm_postProcess", Object(Civi\Core\Event\GenericHookEvent))
 #7 C:\sites\all\modules\civicrm\vendor\symfony\event-dispatcher\Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher.php(167):
 Symfony\Component\EventDispatcher\EventDispatcher->dispatch("hook_civicrm_postProcess",
 Object(Civi\Core\Event\GenericHookEvent))
 #8 C:\sites\all\modules\civicrm\Civi\Core\CiviEventDispatcher.php(47): Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch("hook_civicrm_postProcess",
 Object(Civi\Core\Event\GenericHookEvent))
 #9 C:\sites\all\modules\civicrm\CRM\Utils\Hook.php(164): Civi\Core\CiviEventDispatcher->dispatch("hook_civicrm_postProcess",
 Object(Civi\Core\Event\GenericHookEvent))
 #10 C:\sites\all\modules\civicrm\CRM\Utils\Hook.php(444): CRM_Utils_Hook->invoke((Array:2), "CRM_Event_Form_Participant",
 Object(CRM_Event_Form_Participant), NULL, NULL, NULL, NULL,
 "civicrm_postProcess")
 #11 C:\sites\all\modules\civicrm\CRM\Core\Form.php(516): CRM_Utils_Hook::postProcess("CRM_Event_Form_Participant",
 Object(CRM_Event_Form_Participant))
 #12 C:\sites\all\modules\civicrm\CRM\Core\Form.php(490): CRM_Core_Form->postProcessHook()
 #13 C:\sites\all\modules\civicrm\CRM\Core\QuickForm\Action\Upload.php(169):
 CRM_Core_Form->mainProcess()
 #14 C:\sites\all\modules\civicrm\CRM\Core\QuickForm\Action\Upload.php(136):
CRM_Core_QuickForm_Action_Upload->realPerform(Object(CRM_Event_Form_Participant),
 "upload")
 #15 C:\sites\all\modules\civicrm\packages\HTML\QuickForm\Controller.php(203):
 CRM_Core_QuickForm_Action_Upload->perform(Object(CRM_Event_Form_Participant),
 "upload")
 #16 C:\sites\all\modules\civicrm\packages\HTML\QuickForm\Page.php(103):
 HTML_QuickForm_Controller->handle(Object(CRM_Event_Form_Participant),
 "upload")
 #17 C:\sites\all\modules\civicrm\CRM\Core\Controller.php(351): HTML_QuickForm_Page->handle("upload")
 #18 C:\sites\all\modules\civicrm\CRM\Event\Page\Tab.php(118): CRM_Core_Controller->run()
 #19 C:\sites\all\modules\civicrm\CRM\Event\Page\Tab.php(175): CRM_Event_Page_Tab->edit()
 #20 C:\sites\all\modules\civicrm\CRM\Core\Invoke.php(309): CRM_Event_Page_Tab->run((Array:3), NULL)
 #21 C:\sites\all\modules\civicrm\CRM\Core\Invoke.php(84): CRM_Core_Invoke::runItem((Array:15))
 #22 C:\sites\all\modules\civicrm\CRM\Core\Invoke.php(52): CRM_Core_Invoke::_invoke((Array:3))
 #23 C:\sites\all\modules\civicrm\drupal\civicrm.module(445): CRM_Core_Invoke::invoke((Array:3))
 #24 C:\includes\menu.inc(527): civicrm_invoke("participant", "add")
 #25 C:\index.php(22): menu_execute_active_handler()
 #26 {main}

Answer 1

From the backtrace, you can see that the error is caused by a line in the org.civicrm.multidomaininvoicing extension. I assume this is your extension?

getvalue is only appropriate if you're sure that a value exists; in this case, you made an API call for a value that doesn't exist. If this is a possibility in your scenario, instead use get and search the values array for your result (with error handling to deal with a missing value.