From e905534ea635637a803981a292869cde585f8239 Mon Sep 17 00:00:00 2001
From: Peter Conrad <conrad@quisquis.de>
Date: Sun, 6 Aug 2017 14:20:04 +0200
Subject: [PATCH] Fixed undo_database

---
 libraries/db/undo_database.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/libraries/db/undo_database.cpp b/libraries/db/undo_database.cpp
index b37b2c7d..c5f2ef65 100644
--- a/libraries/db/undo_database.cpp
+++ b/libraries/db/undo_database.cpp
@@ -118,8 +118,6 @@ void undo_database::undo()
       _db.insert( std::move(*item.second) );
 
    _stack.pop_back();
-   if( _stack.empty() )
-      _stack.emplace_back();
    enable();
    --_active_sessions;
 } FC_CAPTURE_AND_RETHROW() }
@@ -127,6 +125,12 @@ void undo_database::undo()
 void undo_database::merge()
 {
    FC_ASSERT( _active_sessions > 0 );
+   if( _active_sessions == 1 && _stack.size() == 1 )
+   {
+      _stack.pop_back();
+      --_active_sessions;
+      return;
+   }
    FC_ASSERT( _stack.size() >=2 );
    auto& state = _stack.back();
    auto& prev_state = _stack[_stack.size()-2];