When selecting a fallback menu in `wp_nav_menu()`, the "first" menu is retrieved from an unsorted query. When retrieving a fallback menu, pass `array( 'orderby' => 'name' )` to `wp_get_nav_menus()` to return a menu consistently.

Props lukecarbis.
Fixes #28126.

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git-svn-id: http://core.svn.wordpress.org/trunk@28630 1a063a9b-81f0-0310-95a4-ce76da25c4cd