From 780418435a58fc0367554db0df912cde37acc29f Mon Sep 17 00:00:00 2001
From: Vojtech Bubnik <bubnikv@gmail.com>
Date: Mon, 7 Dec 2020 17:09:02 +0100
Subject: [PATCH] Fix of Custom profiles prevent the slicer from starting up
 #4996 Creative user made a profile inherit from itself.

---
 src/libslic3r/Preset.cpp | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/libslic3r/Preset.cpp b/src/libslic3r/Preset.cpp
index 37575953d5..cde517aca1 100644
--- a/src/libslic3r/Preset.cpp
+++ b/src/libslic3r/Preset.cpp
@@ -991,7 +991,15 @@ const Preset* PresetCollection::get_preset_parent(const Preset& child) const
 		if (it != m_presets.end()) 
 			preset = &(*it);
     }
-    return (preset == nullptr/* || preset->is_default */|| preset->is_external) ? nullptr : preset;
+    return 
+         // not found
+        (preset == nullptr/* || preset->is_default */|| 
+         // this should not happen, user profile should not derive from an external profile
+         preset->is_external ||
+         // this should not happen, however people are creative, see GH #4996
+         preset == &child) ? 
+            nullptr : 
+            preset;
 }
 
 // Return vendor of the first parent profile, for which the vendor is defined, or null if such profile does not exist.