UsdOutput::IsOutput should check attr validity

diff --git a/pxr/usd/usdShade/output.cpp b/pxr/usd/usdShade/output.cpp
index eb6b33a2b3b8dc7d9290e7ae8550715741a15a62..295f5e97113592f8f8f57bdd5d2387af340801b5 100644 (file)
--- a/pxr/usd/usdShade/output.cpp
+++ b/pxr/usd/usdShade/output.cpp
@@ -181,7 +181,8 @@ UsdShadeOutput::ClearSdrMetadataByKey(const TfToken &key) const
 bool 
 UsdShadeOutput::IsOutput(const UsdAttribute &attr)
 {
-    return TfStringStartsWith(attr.GetName().GetString(), 
+    return attr && attr.IsDefined() &&
+        TfStringStartsWith(attr.GetName().GetString(),
                               UsdShadeTokens->outputs);
 }