From 3888cab96249c40d609bcdcd0c88c9596a881abf Mon Sep 17 00:00:00 2001
From: John Lewin <lewin76@gmail.com>
Date: Wed, 18 Jul 2018 14:59:36 -0700
Subject: [PATCH] Fix observed exception

---
 MatterControl.OpenGL/GCodeRenderer/GCodeRenderer.cs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/MatterControl.OpenGL/GCodeRenderer/GCodeRenderer.cs b/MatterControl.OpenGL/GCodeRenderer/GCodeRenderer.cs
index 48c8633e6..5b570a169 100644
--- a/MatterControl.OpenGL/GCodeRenderer/GCodeRenderer.cs
+++ b/MatterControl.OpenGL/GCodeRenderer/GCodeRenderer.cs
@@ -343,7 +343,8 @@ namespace MatterHackers.GCodeVisualizer
 					for (int i = renderInfo.StartLayerIndex; i < renderInfo.EndLayerIndex - 1; i++)
 					{
 						int featuresOnLayer = renderFeatures[i].Count;
-						if (featuresOnLayer > 1)
+						if (featuresOnLayer > 1
+							&& layerVertexBuffer[i] != null)
 						{
 							layerVertexBuffer[i].RenderRange(0, featureEndIndex[i][featuresOnLayer - 1]);
 						}
@@ -372,7 +373,8 @@ namespace MatterHackers.GCodeVisualizer
 						startFeature = Math.Max(endFeature - 1, 0);
 					}
 
-					if (endFeature > startFeature)
+					if (endFeature > startFeature
+						&& layerVertexBuffer[layerIndex] != null)
 					{
 						int ellementCount = featureEndIndex[layerIndex][endFeature - 1] - featureStartIndex[layerIndex][startFeature];