Various bug fixes

* Clean up master preview render data
* Add size check to IndexSet.Contains

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/PreviewManager.cs

             }
         }
 
+        void DestroyRenderData(PreviewRenderData renderData)
+        {
+            if (renderData.shaderData.shader != null && renderData.shaderData.shader != m_UberShader)
+                Object.DestroyImmediate(renderData.shaderData.shader, true);
+            if (renderData.renderTexture != null)
+                Object.DestroyImmediate(renderData.renderTexture, true);
+            var node = renderData.shaderData.node;
+            if (node != null)
+                node.onModified -= OnNodeModified;
+        }
+
-                if (renderData.shaderData.shader != null && renderData.shaderData.shader != m_UberShader)
-                    Object.DestroyImmediate(renderData.shaderData.shader, true);
-                if (renderData.renderTexture != null)
-                    Object.DestroyImmediate(renderData.renderTexture, true);
-                var node = renderData.shaderData.node;
-                if (node != null)
-                    node.onModified -= OnNodeModified;
+                if (masterRenderData != null && masterRenderData.shaderData != null && masterRenderData.shaderData.node == renderData.shaderData.node)
+                    masterRenderData.shaderData = m_RenderDatas.Where(x => x != null && x.shaderData.node is IMasterNode).Select(x => x.shaderData).FirstOrDefault();
+
+                DestroyRenderData(renderData);
 
                 m_TimeDependentPreviews.Remove(nodeId.index);
                 m_DirtyPreviews.Remove(nodeId.index);
-
-                if (masterRenderData.shaderData != null && masterRenderData.shaderData.node == node)
-                    masterRenderData.shaderData = m_RenderDatas.Where(x => x != null && x.shaderData.node is IMasterNode).Select(x => x.shaderData).FirstOrDefault();
-
-                renderData.shaderData.shader = null;
-                renderData.renderTexture = null;
-                renderData.texture = null;
-                renderData.onPreviewChanged = null;
             }
         }
 
                 m_SceneResources.Dispose();
                 m_SceneResources = null;
             }
-            foreach (var renderData in m_RenderDatas.ToList())
-                DestroyPreview(renderData.shaderData.node.tempId);
+            if (m_MasterRenderData != null)
+                DestroyRenderData(m_MasterRenderData);
+            foreach (var renderData in m_RenderDatas.ToList().Where(x => x != null))
+                DestroyRenderData(renderData);
+            m_RenderDatas.Clear();
         }
 
         public void Dispose()

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Views/PreviewSceneResources.cs

             light1.color = new Color(.4f, .4f, .45f, 0f) * .7f;
 
             m_CheckerboardMaterial = new Material(Shader.Find("Hidden/Checkerboard"));
-            checkerboardMaterial.shader.hideFlags = HideFlags.HideAndDontSave;
             checkerboardMaterial.hideFlags = HideFlags.HideAndDontSave;
 
             if (s_Meshes[0] == null)
 
             if (checkerboardMaterial != null)
             {
-                UnityEngine.Object.DestroyImmediate(checkerboardMaterial);
+                UnityEngine.Object.DestroyImmediate(checkerboardMaterial, true);
                 m_CheckerboardMaterial = null;
             }
 

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Util/IndexSet.cs

         {
             var maskIndex = index >> 5;
             var bitIndex = index & 31;
-            return (m_Masks[maskIndex] & ((uint)1 << bitIndex)) > 0;
+            return maskIndex < m_Masks.Count && (m_Masks[maskIndex] & ((uint)1 << bitIndex)) > 0;
         }
 
         public void CopyTo(int[] array, int arrayIndex)

MaterialGraphProject/ProjectSettings/ProjectVersion.txt

-m_EditorVersion: 2018.1.0b2
+m_EditorVersion: 2018.1.0b1