Error Message When Submitting Lead With Web To Lead Form

I have a web to lead form on a landing page, and when the submit button is clicked, the lead shows up correctly in my Leads Module, but the following message appears on the screen of the landing page where I embedded the form:

Warning: Creating default object from empty value in /home4/sdhronec/public_html/crm/modules/Campaigns/WebToLeadCapture.php on line 126

What is this and how can I fix it?