Fix warning message on node

Author: ecarriou

src/systems/core/system-runtime.json

@@ -10,7 +10,7 @@
       "_id": "1cb9d103d41dd97",
       "component": "e89c617b6b15d24",
       "state": "start",
-      "action": "function start() {\n  document.addEventListener('DOMContentLoaded', function(e) {\n    var systems = [],\n      system = null,\n      scripts = [],\n      script = null,\n      logLevel = 'warn',\n      i = 0,\n      length = 0;\n  \n    // in a browser\n    if (typeof document !== 'undefined') {\n      systems = document.querySelectorAll('link[rel=system]');\n      length = systems.length;\n  \n      // logger\n      scripts = document.querySelectorAll('script[log]');\n      if (scripts.length) {\n        logLevel = scripts[0].getAttribute('log');\n        this.require('logger').level(logLevel);\n      }\n  \n      // systems\n      for (i = 0; i < length; i++) {\n        system = systems[i];\n  \n        if (system.getAttribute('async') === 'false') {\n          this.require('runtime').install(system.href, false);\n        } else {\n          this.require('runtime').install(system.href, true);\n        }\n      }\n  \n      // ready event\n      if (length === 0) {\n        this.require('runtime').ready();\n      }\n    }\n  }.bind(this));\n}",
+      "action": "function start() {\n  if (typeof document !== 'undefined') {\n    document.addEventListener('DOMContentLoaded', function DOMContentLoaded(e) {\n      var systems = [],\n        system = null,\n        scripts = [],\n        script = null,\n        logLevel = 'warn',\n        i = 0,\n        length = 0;\n    \n      systems = document.querySelectorAll('link[rel=system]');\n      length = systems.length;\n  \n      // logger\n      scripts = document.querySelectorAll('script[log]');\n      if (scripts.length) {\n        logLevel = scripts[0].getAttribute('log');\n        this.require('logger').level(logLevel);\n      }\n  \n      // systems\n      for (i = 0; i < length; i++) {\n        system = systems[i];\n  \n        if (system.getAttribute('async') === 'false') {\n          this.require('runtime').install(system.href, false);\n        } else {\n          this.require('runtime').install(system.href, true);\n        }\n      }\n  \n      // ready event\n      if (length === 0) {\n        this.require('runtime').ready();\n      }\n  }.bind(this));\n  }\n}",
       "useCoreAPI": true,
       "core": true
     }