validation BUGFIX appending to empty data tree
diff --git a/src/validation.c b/src/validation.c
index 7b586a5..1219d89 100644
--- a/src/validation.c
+++ b/src/validation.c
@@ -1101,7 +1101,7 @@
         if (!mod) {
             break;
         }
-        if (first == *tree) {
+        if (!first || (first == *tree)) {
             /* make sure first2 changes are carried to tree */
             first2 = tree;
         } else {