Error with Custom post type page with custom loop showing custom post taxonomy term by slug

I have a website with custom post type Pages called ‘mini_site_page’
I also created a custom post taxonomy in Posts called ‘mini_site’ and I check taxonomy inside the custom pages
I want to show inside custom pages a custom loop with taxonomy term checked inside custom pages

This code seems to work but with wp_debug ‘true’ I have this error:

Only variables should be passed by reference in /public_html/wp-content/themes/[website]/[page_template].php on line 132

Do you have some suggestions?