Only variables should be passed by reference

Note: For the interests of clarity, in the issue summary I had changed the path from what was really specified in the warning message, to a more typical xampp/htdocs/public_html. Actually, as you can see by the image I've included with this message, I have xampp pointing to a virtual directory in my windows "My Documents" folder. I have also used underscores in this path (to facilitate sorting). I thought more and decided this might be relevant to the issue.

So, the actual path in the error message is: Strict warning: Only variables should be passed by reference in theme_submenu_tree_teasers() (line 630 of C:\Users\Kevin\Documents\_app-BcResources\_app-BcR\sites\all\modules\submenutree\submenutree.module)