fix error in statuspage if cookies are disabled (#912)

If cookies are disabled, the Statuspage only displays an empty ("Not connected")
This checks if the localStorage API is available and working and only uses it in this case
Also allows better backwards compatibility.

package/gluon-status-page/src/js/main.js

@@ -83,7 +83,17 @@ require([ "bacon"
     return a
   }
 
-  if (localStorage.nodes)
+  var lsavailable = false
+  try {
+    localStorage.setItem("t", "t")
+    localStorage.removeItem("t")
+    lsavailable = true
+  } catch(e) {
+    lsavailable = false
+  }
+
+
+  if ( lsavailable && localStorage.nodes)
     JSON.parse(localStorage.nodes).forEach(nodesBusIn.push)
 
   nodesBus.map(".nodes").onValue(function (nodes) {
@@ -92,6 +102,7 @@ require([ "bacon"
     for (var k in nodes)
       out.push(nodes[k])
 
+    if (lsavailable)
       localStorage.nodes = JSON.stringify(out)
   })