implemented adding/updating of item properties

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

frontend/src/routes/stock/Index.svelte

@@ -35,6 +35,7 @@
             var json = await res.json();
             var dict = {}
             for (var entry of json.sort((a,b) => b.id - a.id)) dict[entry.name+'.'+entry.unit] = entry;
+            properties = null;
             properties = Object.values(dict).sort((a,b) => a.name.localeCompare(b.name));
             yikes();
         } else error(res);