From 1ef03c5cb83d91938ee809309f09d2d42c703c95 Mon Sep 17 00:00:00 2001
From: Benedikt Kloss <bkloss@flatironinstitute.org>
Date: Wed, 24 Jan 2024 19:13:00 -0500
Subject: [PATCH] Populate ITensor with zeros if empty after contracting with
 ProjTTN.

---
 src/treetensornetworks/projttns/abstractprojttn.jl | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/treetensornetworks/projttns/abstractprojttn.jl b/src/treetensornetworks/projttns/abstractprojttn.jl
index 9f6da826..09966f08 100644
--- a/src/treetensornetworks/projttns/abstractprojttn.jl
+++ b/src/treetensornetworks/projttns/abstractprojttn.jl
@@ -80,6 +80,10 @@ function contract(P::AbstractProjTTN, v::ITensor)::ITensor
   for it in itensor_map
     Hv *= it
   end
+  if isempty(Hv)
+    Hv = similar(v)
+    Hv .= 0
+  end
   return Hv
 end