MessageViewer::BlockMailTrackingUrlInterceptor::MailTrackerBlackList causes email not to be displayed

Hi,

I receive email from one particular person which does not display for me in KMail. When I 
click on their email, all I see is "HTML Message" in the message panel and the following in 
the logs for kmail :

QObject::connect: Cannot queue arguments of type 
'MessageViewer::BlockMailTrackingUrlInterceptor::MailTrackerBlackList' 


https://api.kde.org/4.x-api/pim-apidocs/messagelib/messageviewer/src/html/
blockmailtrackingurlinterceptor_8cpp_source.html

which made me re-read the original message content by using "View Source" and in the 
message is the url "http://t.sidekickopen24.com" .

So I'm wondering:
1) is there a bug in the code as I'd expect to see this email but the link to the mailtracker to 
be inactive ?
2) is there an option to turn this check off ?

Or am I missing something ?

Thanks in advance,
Con