Notice: Undefined index: summary in options_validate()

Issue: Notice: Undefined index: summary in options_validate() prevents ajax functionality of contextual filters when creating/editing a view.
This occurs if the view is of a type that does not supply a 'summary' action for absent arguments.

views/handlers/views_handler_argument.inc

class views_handler_argument

  /**
   * Provide a list of default behaviors for this argument if the argument
   * is not present.
   *
   * Override this method to provide additional (or fewer) default behaviors.
   */
function default_actions($which = NULL) {

A module (in my case search_api) can override the default_actions function and not provide a 'summary' action.
In that case the form to define what should happen when the contextual filter argument is missing does not have the 'summary' option.
But views_handler_argument functions options_validate() and options_submit() assume $form_state['values']['options']['summary'] is present and filled.

Attached is a patch that adds an isset check to see if there are actually any summary options before using them.