fix(userspace/libsinsp): set filtercheck list desturctor as virtual

Signed-off-by: Jason Dellaluce <jasondellaluce@gmail.com>

userspace/libsinsp/filter_check_list.h

@@ -32,7 +32,7 @@ class filter_check_list
 {
 public:
 	filter_check_list();
-	~filter_check_list();
+	virtual ~filter_check_list();
 	void add_filter_check(sinsp_filter_check* filter_check);
 	void get_all_fields(std::vector<const filter_check_info*>& list);
 	sinsp_filter_check* new_filter_check_from_another(sinsp_filter_check *chk);