Problems when running Node-RED headless

I'm running Node-RED v0.20.5 on a Ubuntu 18 Virtual Machine with Node.js v8.10.0,

I have created a very simple flow that emails me every 2 minutes to make sure the flow gets properly run. When I start my Node-RED with the command "node-red Email.json", Everything works properly and I get the emails.

The problem comes when I set httpRoot to false on the settings file. When I set it to false and run the same command as before, I get this on the terminal:

pedrojg@pedrojg-VirtualBox:~$ node-red Email.json
23 May 11:34:20 - [info]

Welcome to Node-RED

23 May 11:34:20 - [info] Node-RED version: v0.20.5
23 May 11:34:20 - [info] Node.js version: v8.10.0
23 May 11:34:20 - [info] Linux 4.15.0-50-generic x64 LE
23 May 11:34:21 - [info] Loading palette nodes
23 May 11:34:21 - [warn] rpi-gpio : Raspberry Pi specific node set inactive
23 May 11:34:21 - [warn] rpi-gpio : Cannot find Pi RPi.GPIO python library
23 May 11:34:22 - [warn] ------------------------------------------------------
23 May 11:34:22 - [warn] [node-red/inject] Error: Route.post() requires a callback function but got a [object Undefined] (line:113)
23 May 11:34:22 - [warn] [node-red/debug] Error: Route.post() requires a callback function but got a [object Undefined] (line:151)
23 May 11:34:22 - [warn] [node-red/rpi-gpio] Error: Route.get() requires a callback function but got a [object Undefined] (line:364)
23 May 11:34:22 - [warn] [node-red/udp] Error: Route.get() requires a callback function but got a [object Undefined] (line:133)
23 May 11:34:22 - [warn] ------------------------------------------------------
23 May 11:34:22 - [info] Settings file : /home/pedrojg/.node-red/settings.js
23 May 11:34:22 - [info] Context store : 'default' [module=memory]
23 May 11:34:22 - [info] User directory : /home/pedrojg/.node-red
23 May 11:34:22 - [warn] Projects disabled : editorTheme.projects.enabled=false
23 May 11:34:22 - [info] Flows file : /home/pedrojg/.node-red/Email.json
23 May 11:34:22 - [info] Running in headless mode
23 May 11:34:22 - [warn]


Your flow credentials file is encrypted using a system-generated key.

If the system-generated key is lost for any reason, your credentials
file will not be recoverable, you will have to delete it and re-enter
your credentials.

You should set your own key using the 'credentialSecret' option in
your settings file. Node-RED will then re-encrypt your credentials
file using your chosen key the next time you deploy a change.

23 May 11:34:22 - [info] Waiting for missing types to be registered:
23 May 11:34:22 - [info] - inject

Do you have any ideas as to why this could be and how to solve it?
I have tried installing "Inject" again to see if that was the problem, but it seems that it wasn't.
Any help would be appreciated, thanks!

This is a known bug: https://github.com/node-red/node-red/issues/2166

A fix has been provided, but we haven't merged it yet. I hadn't planned on doing another maintenance release on 0.20.x for a while as I'm trying to get the first beta for 1.0.0 ready. But if this is blocking you we can look at doing one sooner rather than later.

Thanks for your early reply. I don't need a maintenance release, since there is a local fix provided in the Issue you linked me that made it work