suggestions

block.php

$new_region = NULL;
    if (!isset($regions[$this->region]) && $this->status()) {
      if (isset($this->original)) {
        $original_region = $this->original->getRegion();
        // If \Drupal\block\BlockInterface::BLOCK_REGION_NONE was used to
        // disable the block and we have an original region then keep in the
        // block in the original region.
        if (isset($regions[$original_region]) && $this->region == BlockInterface::BLOCK_REGION_NONE) {
          $new_region = $original_region;
        }
      }
      if (!$new_region) {
        $new_region = system_default_region($this->theme);
      }
      $this
        ->setRegion($new_region)
        ->disable();
    }