Error link

Good evening are a user with License to mailpoet payment.
I see an error every time I create a connection between the link ‘ and email and web content. The error is as follows:

HOME /
CATCHABLE FATAL ERROR: OBJECT OF CLASS WP_ERROR COULD NOT BE CONVERTED TO STRING IN /HOME/WEBTECNI/DOMAINS/WEBTECNICA.IT/PUBLIC_HTML/WP-CONTENT/THEMES/OPTIMAS/INCLUDES/BREADCRUMBS.PHP ON LINE 46

https://www.ads-software.com/plugins/wysija-newsletters/