Error on subscribing via subscribe-block

I received same thing but can't be sure on origination looks like someone was subscribing
PDOException: SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'nid' cannot be null: INSERT INTO {simplenews_statistics} (nid, send) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1); Array ( [:db_insert_placeholder_0] => [:db_insert_placeholder_1] => 1 ) in simplenews_statistics_mail_alter() (line 175 of/...../public_html/sites/all/modules/simplenews_statistics/simplenews_statistics.module).

Error Preceded by these warnings.

Notice: Trying to get property of non-object in simplenews_statistics_mail_alter() (line 150 of /......../public_html/sites/all/modules/simplenews_statistics/simplenews_statistics.module).

Notice: Undefined index: node in simplenews_statistics_mail_alter() (line 150 of /......./public_html/sites/all/modules/simplenews_statistics/simplenews_statistics.module).

Update Edit: The above seemed to have been caused by someone trying to subscribe. I tried to subscribe too and the system came back with web site error message. So I turned off the Stt package and all is sort of OK again.

Commented on wrong issue, please ignore

D7 code is unstable and will be rewritten soon.