Make gltf2 export normal normalization safe

This avoids introducing NaNs e.g. when the input mesh has 0-length normals

code/AssetLib/glTF/glTFExporter.cpp

@@ -348,7 +348,7 @@ void glTFExporter::GetMatColorOrTex(const aiMaterial* mat, glTF::TexProperty& pr
 
                     if (path[0] == '*') { // embedded
                         aiTexture* curTex = mScene->mTextures[atoi(&path[1])];
-						
+
                         prop.texture->source->name = curTex->mFilename.C_Str();
 
                         uint8_t *data = reinterpret_cast<uint8_t *>(curTex->pcData);

code/AssetLib/glTF2/glTF2Exporter.cpp

@@ -758,7 +758,7 @@ void glTF2Exporter::ExportMeshes()
         // Normalize all normals as the validator can emit a warning otherwise
         if ( nullptr != aim->mNormals) {
             for ( auto i = 0u; i < aim->mNumVertices; ++i ) {
-                aim->mNormals[ i ].Normalize();
+                aim->mNormals[ i ].NormalizeSafe();
             }
         }