Ensure blocks exist on node update

Problem/Motivation

Because of some reason, the frontend theme of a website was marked as inactive by list_themes(). This means no entries in the block table were created when a new node was created of a node type which has nodeblock enabled, but an entry in the nodeblock table will exist.

Steps to reproduce

Enable a new theme and resave a node. A entry in the block table will not be created, but an entry in the nodeblock table exists.

Proposed resolution

Ensure that entries in the block table exist in hook_node_update. See the attached patch.