If you want to delete everything from the user menu you get an explosion.

Notice: Undefined variable: children in /home/damyonw/Documents/Moodle/integration/master/moodle/user/lib.php on line 687
Call Stack

1. Time Memory Function Location
   1 0.0000 236360 {main}( ) ../search.php:0
   2 1.7239 22514232 core_renderer->header( ) ../search.php:36
   3 1.7300 22548928 core_renderer->render_page_layout( ) ../outputrenderers.php:845
   4 1.7301 22590544 include( '/home/damyonw/Documents/Moodle/integration/master/moodle/theme/clean/layout/columns2.php' ) ../outputrenderers.php:915
   5 1.8061 23227288 core_renderer->user_menu( ) ../columns2.php:53
   6 1.8062 23229840 user_get_user_navigation_info( ) ../outputrenderers.php:2978
   7 1.8072 23238792 user_convert_text_to_menu_items( ) ../lib.php:869
   
   ( ! ) Warning: Invalid argument supplied for foreach() in /home/damyonw/Documents/Moodle/integration/master/moodle/user/lib.php on line 870
   Call Stack
   # Time Memory Function Location
   1 0.0000 236360 {main}

   ( ) ../search.php:0
   2 1.7239 22514232 core_renderer->header( ) ../search.php:36
   3 1.7300 22548928 core_renderer->render_page_layout( ) ../outputrenderers.php:845
   4 1.7301 22590544 include( '/home/damyonw/Documents/Moodle/integration/master/moodle/theme/clean/layout/columns2.php' ) ../outputrenderers.php:915
   5 1.8061 23227288 core_renderer->user_menu( ) ../columns2.php:53
   6 1.8062 23229840 user_get_user_navigation_info( ) ../outputrenderers.php:2978