From 706b74a15b49f9f1a721ab8a602b602c7f1e5e96 Mon Sep 17 00:00:00 2001
From: Krasimir Angelov <kr.angelov@gmail.com>
Date: Sat, 8 Oct 2022 08:08:30 +0200
Subject: [PATCH] bugfix: check for 0 before free_ref

---
 src/runtime/c/pgf/pgf.cxx | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/runtime/c/pgf/pgf.cxx b/src/runtime/c/pgf/pgf.cxx
index 8b9a7c56c..000a136b0 100644
--- a/src/runtime/c/pgf/pgf.cxx
+++ b/src/runtime/c/pgf/pgf.cxx
@@ -615,7 +615,8 @@ PgfExpr pgf_read_expr(PgfText *input, PgfUnmarshaller *u)
     PgfExprParser parser(input, u);
     PgfExpr res = parser.parse_expr();
     if (!parser.eof()) {
-        u->free_ref(res);
+        if (res != 0)
+            u->free_ref(res);
         return 0;
     }
     return res;