From 0911de76eb6ac6d8fded05b26cce1a343aac0a50 Mon Sep 17 00:00:00 2001
From: Adam Nelson <nelsonag@umich.edu>
Date: Sat, 28 Nov 2015 20:18:13 -0500
Subject: [PATCH] Added MGXS support for void materials

---
 src/tracking.F90 | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/tracking.F90 b/src/tracking.F90
index 028ec3ee6c..24ade265be 100644
--- a/src/tracking.F90
+++ b/src/tracking.F90
@@ -91,8 +91,15 @@ contains
       else
         ! Since the MGXS can be angle dependent, this needs to be done
         ! After every collision for the MGXS mode
-        call calculate_mgxs(macro_xs(p % material) % obj, p % g, &
-                            p % coord(p % n_coord) % uvw, material_xs)
+        if (p % material /= MATERIAL_VOID) then
+          call calculate_mgxs(macro_xs(p % material) % obj, p % g, &
+                              p % coord(p % n_coord) % uvw, material_xs)
+        else
+          material_xs % total      = ZERO
+          material_xs % elastic    = ZERO
+          material_xs % absorption = ZERO
+          material_xs % nu_fission = ZERO
+        end if
       end if
 
       ! Find the distance to the nearest boundary