Undefined array key "downloadURL" in metastore process node data

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Describe the bug

If a site has distributions with an accessUrl and no downloadUrl the undefined key error below appears. This is from metastore module's theme.inc file were some variables for themeing and a table are created.

Warning: Undefined array key "downloadURL" in metastore_preprocess_node__data() (line 101 of /var/www/html/docroot/modules/contrib/dkan/modules/metastore/metastore.theme.inc)

Steps To Reproduce

Build a new DKAN site with a schema that doesn't require downloadUrl key in the distribution objects.
Import data and check for the errors after a page render.

Expected behavior

This shouldn't cause an error if the key doesn't exist.