bus: implement support for FD passing

src/shared/util.c

@@ -219,6 +219,8 @@ void close_nointr_nofail(int fd) {
 void close_many(const int fds[], unsigned n_fd) {
         unsigned i;
 
+        assert(fds || n_fd <= 0);
+
         for (i = 0; i < n_fd; i++)
                 close_nointr_nofail(fds[i]);
 }