Thomas, it is optional and much discussed online. 

I listen to a lot of material which includes speakers from several regions of France, and the liaison following ‘trop’  is commonly but not universally used by them.  It seems quite common in the East of France, which is the regional accent I am most exposed to. 

I have also included a link to an external blog that includes discussion of  the optional liaison after ‘trop’ more specifically.

https://french.stackexchange.com/questions/43043/is-trop-occupé-pronunced-troccupé-or-tropoccupé

 https://www.fluentu.com/blog/french/liaison-french/