make tdestroy allow null function pointer if no destructor is needed

this change is to align with a change in the glibc interface.

diff --git a/src/search/tdestroy.c b/src/search/tdestroy.c
index 6f430bd..5f9e197 100644 (file)
--- a/src/search/tdestroy.c
+++ b/src/search/tdestroy.c
@@ -16,6 +16,6 @@ void tdestroy(void *root, void (*freekey)(void *))
                return;
        tdestroy(r->left, freekey);
        tdestroy(r->right, freekey);
-       freekey(r->key);
+       if (freekey) freekey(r->key);
        free(r);
 }