diff -r bbadf84cfc2d -r 4d7a2238c5ac dav/sync.c
--- a/dav/sync.c	Sun May 21 11:52:06 2023 +0200
+++ b/dav/sync.c	Sun May 21 16:34:58 2023 +0200
@@ -36,8 +36,10 @@
 #include <utime.h>
 #include <libxml/xmlerror.h>
 #include <sys/types.h>
+#include <cx/map.h>
 #include <cx/string.h>
 #include <cx/utils.h>
+#include <cx/list.h>
 #include <cx/hash_map.h>
 #include <cx/printf.h>
 #include <dirent.h>
@@ -115,45 +117,12 @@
 
 
 
-
-static bool nulliter_valid(void const *d) {
-    return false;
-}
-
-static void * nulliter_current(void const *d) {
-    return NULL;
-}
-
-void * nulliter_current_impl(void const *d) {
-    return NULL;
-}
-
-void nulliter_next(void *d) {
-    // noop
-}
-
-bool nulliter_flag_removal(void *d) {
-    return false;
-}
-
-
-static CxIterator nullIterator(void) {
-    CxIterator iter;
-    memset(&iter, 0, sizeof(CxIterator));
-    iter.base.valid = nulliter_valid;
-    iter.base.current = nulliter_current;
-    iter.base.current_impl = nulliter_current_impl;
-    iter.base.next = nulliter_next;
-    iter.base.flag_removal = nulliter_flag_removal;
-    return iter;
-}
-
 static CxIterator mapIteratorValues(CxMap *map) {
-    return map ? cxMapIteratorValues(map) : nullIterator();
+    return cxMapIteratorValues(map ? map : cxEmptyMap);
 }
 
 static CxIterator listIterator(CxList *list) {
-    return list ? cxListIterator(list) : nullIterator();
+    return cxListIterator(list ? list : cxEmptyList);
 }
 
 typedef void*(*clonefunc)(void *elm, void *userdata);