Fix transaction delete use-after-free, take 2.

The problem with take 1 was that the duplicate split uses the same lot
and account pointers without adding itself to those lists, causing
checks in unit tests to fail.

libgnucash/engine/Split.cpp

@@ -707,6 +707,19 @@ xaccFreeSplit (Split *split)
     CACHE_REMOVE(split->memo);
     CACHE_REMOVE(split->action);
 
+    if (split->inst.e_type) /* Don't do this for dupe splits. */
+    {
+        /* gnc_lot_remove_split needs the account, so do it first. */
+        if (GNC_IS_LOT (split->lot) && !qof_instance_get_destroying (QOF_INSTANCE (split->lot)))
+            gnc_lot_remove_split (split->lot, split);
+        if (GNC_IS_ACCOUNT (split->acc)
+            && !qof_instance_get_destroying (QOF_INSTANCE (split->acc)))
+            gnc_account_remove_split (split->acc, split);
+        /* We should do the same for split->parent but we might be getting
+         * called from xaccFreeTransaction and that would cause trouble.
+         */
+    }
+
     /* Just in case someone looks up freed memory ... */
     split->memo        = (char *) 1;
     split->action      = NULL;