openwrt: update Gluon upgrade script

openwrt/node-whisperer/files/node-whisperer.upgrade.lua

@@ -3,15 +3,30 @@
 local site = require 'gluon.site'
 local uci = require('simple-uci').cursor()
 
+local default_sources = {
+    'hostname',
+    'node_id',
+    'uptime',
+    'site_code',
+    'system_load',
+    'firmware_version',
+}
+
 local sources = {}
 local disabled = false
+local sources_set = false
 
 if not site.node_whisperer.enabled(false) then
     disabled = true
 end
 
 for _, information in ipairs(site.node_whisperer.information({})) do
     table.insert(sources, information)
+    sources_set = true
+end
+
+if not sources_set then
+    sources = default_sources
 end
 
 uci:set('node-whisperer', 'settings', 'disabled', disabled)