Remove st != NULL checks from recursor functions

In the description of 3111908b03, it says
that the functions must be able to handle st being NULL, but recurse
always passes a valid pointer. The only function that was ever passed
NULL was rm(), but this was changed to go through recurse in
2f4ab52739, so now the checks are
pointless.

chown.c

@@ -32,7 +32,7 @@ chownpwgr(const char *path, struct stat *st, void *data, struct recursor *r)
 	if (chownf(path, uid, gid) < 0) {
 		weprintf("%s %s:", chownf_name, path);
 		ret = 1;
-	} else if (st && S_ISDIR(st->st_mode)) {
+	} else if (S_ISDIR(st->st_mode)) {
 		recurse(path, NULL, r);
 	}
 }