From 635dc380a3f45fa70ca297890ba1061508faef13 Mon Sep 17 00:00:00 2001
From: Krasimir Angelov <kr.angelov@gmail.com>
Date: Fri, 24 Jun 2022 06:31:28 +0200
Subject: [PATCH] handle linref when the argument is an unknown function

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

diff --git a/src/runtime/c/pgf/linearizer.cxx b/src/runtime/c/pgf/linearizer.cxx
index 088bb4bf7..af5f72d32 100644
--- a/src/runtime/c/pgf/linearizer.cxx
+++ b/src/runtime/c/pgf/linearizer.cxx
@@ -418,6 +418,8 @@ bool PgfLinearizer::TreeLinrefNode::resolve(PgfLinearizer *linearizer)
 {
     TreeNode *root = args;
     ref<PgfConcrLincat> lincat = root->get_lincat(linearizer);
+    if (lincat == 0)
+        return true;
 
     while (lincat->n_lindefs+lin_index < lincat->res->len) {
         // Unbind all variables