Add DIMM slot table to hardware status page

Add items at /redfish/v1/Systems/system/Memory endpoint to
DIMM slot table. The table is sortable and has a row expansion
to view details. The code is currently missing most properties
needed to match the design. This table will need to be revisited
when all properties are available.

Signed-off-by: Yoshie Muranaka <yoshiemuranaka@gmail.com>
Change-Id: I07cacf3403fe84431cb9fe0e4315069fc7baf27d
diff --git a/src/components/Mixins/TableDataFormatter.js b/src/components/Mixins/TableDataFormatter.js
index 5dbe40a..e811f90 100644
--- a/src/components/Mixins/TableDataFormatter.js
+++ b/src/components/Mixins/TableDataFormatter.js
@@ -1,7 +1,7 @@
 const TableDataFormatter = {
   methods: {
     tableFormatter(value) {
-      if (value === undefined || value === '') {
+      if (value === undefined || value === null || value === '') {
         return '--';
       } else {
         return value;