[kvp-frame.cpp] expose iterator, skip inexistent frame

libgnucash/engine/kvp-frame.cpp

@@ -78,6 +78,8 @@ KvpFrame::get_child_frame_or_nullptr (Path const & path) noexcept
     if (map_iter == m_valuemap.end ())
         return nullptr;
     auto child = map_iter->second->get <KvpFrame *> ();
+    if (!child)
+        return nullptr;
     Path send;
     std::copy (path.begin () + 1, path.end (), std::back_inserter (send));
     return child->get_child_frame_or_nullptr (send);

libgnucash/engine/kvp-frame.hpp

@@ -226,6 +226,9 @@ struct KvpFrameImpl
     bool empty() const noexcept { return m_valuemap.empty(); }
     friend int compare(const KvpFrameImpl&, const KvpFrameImpl&) noexcept;
 
+    map_type::iterator begin() { return m_valuemap.begin(); }
+    map_type::iterator end() { return m_valuemap.end(); }
+
     private:
     map_type m_valuemap;