If you know how to make a patch to fix red errors when one of the supported mods is missing, give me an example here please.

For example, I will give here what one of my patches for other mods looks like.

___<?xml version="1.0" encoding="utf-8"?>
___<Patch>
___
_____<Operation Class="PatchOperationAdd">
______<xpath>*/ThingDef[defName = "RFFBricks"]/stuffProps/statFactors</xpath>
______<value>
_______<Mass>2</Mass>
______</value>
_____</Operation>
___
___</Patch>

This mod is here

Where do I have to put information when supported mod does not exist so that game ignores it?

__hey
____(It exists here because steam hates spaces)
__hey

(These phrases above me with normal spaces instead of "_" look like this)

hey
(It exists here because steam hates spaces)
hey