non-object in simplenews_node_view() when previewing newly created newsletter

Creating new newsletter content (only needs a few words of plain text) and then requesting preview repeatably gives:-

•Notice: Trying to get property of non-object in simplenews_node_view() (line 355 of /content/Hosting/m/s/mshand.org.uk/subdomains/newsletter/web/sites/all/modules/simplenews/simplenews.module).
•Notice: Trying to get property of non-object in simplenews_node_view() (line 355 of /content/Hosting/m/s/mshand.org.uk/subdomains/newsletter/web/sites/all/modules/simplenews/simplenews.module).

Don't get any issues if you save rather than preview.
Nor is there any issue with editting an already created node and then requesting preview.

Repeated previews without saving give the error each time.

The problem seems benign, apart from generating the error message.