From b1fa02bcc8dbe04807ef57c5fa988aa1c2e9a79a Mon Sep 17 00:00:00 2001
From: Jeff Young <jeff@rokeby.ie>
Date: Sat, 20 Mar 2021 11:04:36 +0000
Subject: [PATCH] Push a non-existent ref's value as 0.  (Don't just crash.)

Fixes https://gitlab.com/kicad/code/kicad/issues/7971
---
 common/libeval_compiler/libeval_compiler.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/common/libeval_compiler/libeval_compiler.cpp b/common/libeval_compiler/libeval_compiler.cpp
index 4f812f114c..e45681dd6e 100644
--- a/common/libeval_compiler/libeval_compiler.cpp
+++ b/common/libeval_compiler/libeval_compiler.cpp
@@ -1088,8 +1088,11 @@ void UOP::Exec( CONTEXT* ctx )
     {
     case TR_UOP_PUSH_VAR:
     {
-        auto value = ctx->AllocValue();
-        value->Set( m_ref->GetValue( ctx ) );
+        VALUE* value = ctx->AllocValue();
+
+        if( m_ref )
+            value->Set( m_ref->GetValue( ctx ) );
+
         ctx->Push( value );
     }
         break;