Name::Index(): Fix initialization order

Add the node listener directly after calling the base class Init().
Otherwise, on error, the we could try to remove the listener although it
wasn't added in the first place.

src/add-ons/kernel/file_systems/packagefs/NameIndex.cpp

@@ -148,13 +148,12 @@ NameIndex::Init(Volume* volume)
 	if (error != B_OK)
 		return error;
 
+	fVolume->AddNodeListener(this, NULL);
+
 	fEntries = new(std::nothrow) EntryTree;
 	if (fEntries == NULL)
 		return B_NO_MEMORY;
 
-	fVolume = volume;
-	fVolume->AddNodeListener(this, NULL);
-
 	return B_OK;
 }