[Plugin: Wordbooker] Attempt to modify property of non-object

I started to receive following error in Apache logs:

Attempt to modify property of non-object in …/wp-content/plugins/wordbooker/wordbooker.php on line 1867

This happens when I request the “share a draft” URL of a draft post shared using the “Share a Draft” plugin.

# Wordbooker: 1.8.16
# Wordbooker Schema: 8
# WordPress: 3.0.1
# PHP: 5.3.2
# JSON Encode: PHP
# JSON Decode: PHP
# Curl Status: Curl can access Facebook – All is OK
# Fopen Status: Fopen is available and can access Facebook – All is OK
# JSON Version: 1.2.1
# SimpleXML library: PHP
# HTTP Output Character Encoding: pass
# Internal PHP Character Encoding: UTF-8
# MySQL: 5.0.91
# Facebook Transaction limit: 40
# Database character_set_client : utf8
# Database character_set_connection : utf8
# Database character_set_database : utf8
# Database character_set_filesystem : binary
# Database character_set_results : utf8
# Database character_set_server : utf8
# Database character_set_system : utf8
# Database character_sets_dir : /usr/share/mysql/charsets/
# Database collation_connection : utf8_general_ci
# Database collation_database : utf8_unicode_ci
# Database collation_server : utf8_unicode_ci
# Server : GFE/1.3
# Active Plugins :
CGM Events Calendar ( 0.8.1 )
Dashboard Post-it ( 1.1 )
Flash Video Player ( 5.0.4 )
Google XML Sitemaps ( 3.2.4 )
HeadSpace2 ( 3.6.33 )
Share a Draft ( 1.3 )
SI CAPTCHA Anti-Spam ( 2.6.3 )
WP-EMail ( 2.52 )
WP-UserOnline ( 2.80 )