QueuerService and ProcessorsService assumes there are queuers in CMI

QueuerService.php:84-90

// Override the mapping with information stored in CMI, then filter out
// everything that isn't enabled and finally flip the array with just ids.
foreach ($this->configFactory->get('purge.plugins')->get('queuers') as $inst) {
  if (isset($this->plugins_enabled[$inst['plugin_id']])) {
    $this->plugins_enabled[$inst['plugin_id']] = $inst['status'];
  }
}

This produces a warning on site install: "Invalid argument supplied for foreach() QueuersService.php:86"

Should be updated to something like this:

// Override the mapping with information stored in CMI, then filter out
// everything that isn't enabled and finally flip the array with just ids.
$queuers = $this->configFactory->get('purge.plugins')->get('queuers');
if ($queuers) {
  foreach ($queuers as $inst) {
    if (isset($this->plugins_enabled[$inst['plugin_id']])) {
      $this->plugins_enabled[$inst['plugin_id']] = $inst['status'];
    }
  }
}