trying to improve how data / layout / root and templtae docs are accessed.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/client/util/History.ts b/src/client/util/History.ts
index 9728e3177..0df0ec337 100644
--- a/src/client/util/History.ts
+++ b/src/client/util/History.ts
@@ -94,7 +94,7 @@ export namespace HistoryUtil {
             }
             if (Array.isArray(value)) {
             } else if (parser === true || parser === 'json') {
-                value = JSON.parse(value);
+                value = value === 'undefined' ? undefined : JSON.parse(value);
             } else if (parser === 'none') {
             } else {
                 value = parser(value);