Loads all breakpoints, remove non-existing ones.
array Array containing breakpoints keyed by their id.
protected function loadAllBreakpoints() {
$breakpoints = $this->breakpoints;
$this->breakpoints = array();
foreach ($breakpoints as $breakpoint_id) {
$breakpoint = breakpoint_load($breakpoint_id);
if ($breakpoint) {
$this->breakpoints[$breakpoint_id] = $breakpoint;
}
}
}