After manual migration from nopremium, Undefined index in premium_node_view()

We were having a lot of troubles with the nopremium module so, after some testing, we decided to switch to premium_content. After installing the module, in the database I ran a SQL insert to migrate across all the old nopremium nodes to premium_content like so:

INSERT INTO premium_nodes (nid, level_name, start_ts, end_ts)
    select n.nid, 'member_only_content', 0, 0
    from node n
    where n.premium = 1;

After testing, this worked - node teasers are being shown for premium content with the access denied message, but when error logging is activated I get the following notices (even though it seems to be working fine):

    Notice: Undefined index: body in premium_node_view() (line 70 of /home/example/public_html/sites/all/modules/contrib/premium_content/premium.module).
    Notice: Undefined offset: 0 in premium_node_view() (line 70 of /home/example/public_html/sites/all/modules/contrib/premium_content/premium.module).
    Notice: Undefined index: #markup in premium_node_view() (line 70 of /home/example/public_html/sites/all/modules/contrib/premium_content/premium.module).

Any ideas?