fixing OBJ loading crash when there are no normals present

src/rmodels.c

@@ -4473,9 +4473,17 @@ static Model LoadOBJ(const char *fileName)
 
             for (int i = 0; i < 3; i++) model.meshes[meshIndex].vertices[localMeshVertexCount*3 + i] = objAttributes.vertices[vertIndex*3 + i];
 
-            for (int i = 0; i < 3; i++) model.meshes[meshIndex].normals[localMeshVertexCount*3 + i] = objAttributes.normals[normalIndex*3 + i];
-
             for (int i = 0; i < 2; i++) model.meshes[meshIndex].texcoords[localMeshVertexCount*2 + i] = objAttributes.texcoords[texcordIndex*2 + i];
+            if (objAttributes.normals != NULL && normalIndex != TINYOBJ_INVALID_INDEX && normalIndex >= 0)
+            {
+                for (int i = 0; i < 3; i++) model.meshes[meshIndex].normals[localMeshVertexCount*3 + i] = objAttributes.normals[normalIndex*3 + i];
+            }
+            else
+            {
+                model.meshes[meshIndex].normals[localMeshVertexCount*3 + 0] = 0.0f;
+                model.meshes[meshIndex].normals[localMeshVertexCount*3 + 1] = 1.0f;
+                model.meshes[meshIndex].normals[localMeshVertexCount*3 + 2] = 0.0f;
+            }
 
             model.meshes[meshIndex].texcoords[localMeshVertexCount*2 + 1] = 1.0f - model.meshes[meshIndex].texcoords[localMeshVertexCount*2 + 1];