From 212bf21b2d17150e7ce0dc1229e44c43f6c125c4 Mon Sep 17 00:00:00 2001
From: Vojtech Bubnik <bubnikv@gmail.com>
Date: Tue, 29 Aug 2023 10:56:54 +0200
Subject: [PATCH] Fix of SPE-1849, GH #11174: Access violation error when
 slicing Fixed access of an undefined extruder at the start of G-code export
 from wipe tower generator.

---
 src/libslic3r/GCode.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index 444fe95e25..bf96a035d0 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -3256,7 +3256,7 @@ std::string GCode::travel_to(const Point &point, ExtrusionRole role, std::string
 
 bool GCode::needs_retraction(const Polyline &travel, ExtrusionRole role)
 {
-    if (travel.length() < scale_(EXTRUDER_CONFIG(retract_before_travel))) {
+    if (! m_writer.extruder() || travel.length() < scale_(EXTRUDER_CONFIG(retract_before_travel))) {
         // skip retraction if the move is shorter than the configured threshold
         return false;
     }