mime-settings: Properly quote command parameters
Like 85! just for the 4.16 branch.
I only swapped xfce_str_replace and xfce_str_is_empty by exo_str_replace and exo_str_is_empty, since xfce_* did not exist for 4.16.
@Tamaranch, since your name is on it, better take a look before I push it !
Edited by Alexander Schwinn