Spec says to return null, not throw. Bug 334884, r+sr=sicking

content/base/src/nsDOMLists.cpp

@@ -67,11 +67,11 @@ NS_IMETHODIMP
 nsDOMStringList::Item(PRUint32 aIndex, nsAString& aResult)
 {
   if (aIndex >= (PRUint32)mNames.Count()) {
-    return NS_ERROR_DOM_INDEX_SIZE_ERR;
+    SetDOMStringToNull(aResult);
+  } else {
+    mNames.StringAt(aIndex, aResult);
   }
 
-  mNames.StringAt(aIndex, aResult);
-
   return NS_OK;
 }
 
@@ -112,11 +112,11 @@ NS_IMETHODIMP
 nsNameList::GetName(PRUint32 aIndex, nsAString& aResult)
 {
   if (aIndex >= (PRUint32)mNames.Count()) {
-    return NS_ERROR_DOM_INDEX_SIZE_ERR;
+    SetDOMStringToNull(aResult);
+  } else {
+    mNames.StringAt(aIndex, aResult);
   }
 
-  mNames.StringAt(aIndex, aResult);
-
   return NS_OK;
 }
 
@@ -124,11 +124,11 @@ NS_IMETHODIMP
 nsNameList::GetNamespaceURI(PRUint32 aIndex, nsAString& aResult)
 {
   if (aIndex >= (PRUint32)mNames.Count()) {
-    return NS_ERROR_DOM_INDEX_SIZE_ERR;
+    SetDOMStringToNull(aResult);
+  } else {
+    mNamespaceURIs.StringAt(aIndex, aResult);
   }
 
-  mNamespaceURIs.StringAt(aIndex, aResult);
-
   return NS_OK;
 }