"Invalid argument supplied for foreach"

[rbos]

I was debugging an error today with Islandora, and every initial page load was getting an error.

Warning: Invalid argument supplied for foreach() in Drupal\islandora_breadcrumbs\IslandoraBreadcrumbBuilder->nodeHasReferenceFields() (line 236 of modules/contrib/islandora/modules/islandora_breadcrumbs/src/IslandoraBreadcrumbBuilder.php).

With some digging I figured out that

foreach ($this->config->get('referenceFields')

doesn't always get a non-NULL value.

Casting it to array fixes it.

foreach ((array)$this->config->get('referenceFields')

[rbos]

or obviously if you have a different solution for this issue, I'm open to it. I'm not super familiar with either this module or Islandora. :)