From f93ee9daced8e77227bdeba50fffd5e596eabe99 Mon Sep 17 00:00:00 2001
From: Kim Kulling <kim.kulling@googlemail.com>
Date: Sat, 12 May 2018 08:10:26 +0200
Subject: [PATCH] closes https://github.com/assimp/assimp/issues/1780: check
 against nullptr before accessing normal data in aiMesh instance.

---
 code/glTF2Exporter.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/code/glTF2Exporter.cpp b/code/glTF2Exporter.cpp
index 5376788b2..9bb99b0b0 100644
--- a/code/glTF2Exporter.cpp
+++ b/code/glTF2Exporter.cpp
@@ -728,8 +728,10 @@ void glTF2Exporter::ExportMeshes()
 
 		/******************** Normals ********************/
         // Normalize all normals as the validator can emit a warning otherwise
-        for (auto i = 0u; i < aim->mNumVertices; ++i) {
-            aim->mNormals[i].Normalize();
+        if ( nullptr != aim->mNormals) {
+            for ( auto i = 0u; i < aim->mNumVertices; ++i ) {
+                aim->mNormals[ i ].Normalize();
+            }
         }
 
 		Ref<Accessor> n = ExportData(*mAsset, meshId, b, aim->mNumVertices, aim->mNormals, AttribType::VEC3, AttribType::VEC3, ComponentType_FLOAT);