From a71ee7eb3a3c2e3b2f4d9defa80505eb6196ed4c Mon Sep 17 00:00:00 2001
From: Chris Santora <santorac@amazon.com>
Date: Tue, 20 Jul 2021 13:43:24 -0700
Subject: [PATCH] Fixed the MaterialAssignmentId version converter to properly
 handle the default material assignment slot.

Signed-off-by: santorac <55155825+santorac@users.noreply.github.com>
---
 .../Common/Code/Source/Material/MaterialAssignmentId.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/Gems/Atom/Feature/Common/Code/Source/Material/MaterialAssignmentId.cpp b/Gems/Atom/Feature/Common/Code/Source/Material/MaterialAssignmentId.cpp
index 5db6c4c15c..b8a03af6d1 100644
--- a/Gems/Atom/Feature/Common/Code/Source/Material/MaterialAssignmentId.cpp
+++ b/Gems/Atom/Feature/Common/Code/Source/Material/MaterialAssignmentId.cpp
@@ -33,7 +33,14 @@ namespace AZ
                     // No need to early-return, the object will still load successfully, it will just report more errors about the unrecognized element.
                 }
 
-                classElement.AddElementWithData(context, "materialSlotStableId", materialAssetId.m_subId);
+                if (materialAssetId.IsValid())
+                {
+                    classElement.AddElementWithData(context, "materialSlotStableId", materialAssetId.m_subId);
+                }
+                else
+                {
+                    classElement.AddElementWithData(context, "materialSlotStableId", RPI::ModelMaterialSlot::InvalidStableId);
+                }
             }
 
             return true;