Improve error message for failed conversion in VM
Improve error message for failed conversion in VM

- Fixes #2045

- Old one:
  Error: conversion from unknown type to unknown type is invalid
- New one:
  Error: conversion from -1 to [0..255] is invalid

Dhertz/Nim,haiodo/Nim,nanoant/Nim,jfhg/Nim,endragor/Nim,nanoant/Nim,judofyr/Nim,greyanubis/Nim,sferik/Nim,Matt14916/Nim,sferik/Nim,dom96/Nim,fredericksilva/Nim,kirbyfan64/Nim,fredericksilva/Nim,haiodo/Nim,JCavallo/Nim,BlaXpirit/nim,MrJohz/Nim,haiodo/Nim,Senketsu/Nim,mbaulch/Nim,singularperturbation/Nim,singularperturbation/Nim,nimLuckyBull/Nim,singularperturbation/Nim,msmith491/Nim,russpowers/Nim,Dhertz/Nim,haiodo/Nim,sarvex/Nim-lang,russpowers/Nim,kirbyfan64/Nim,douglas-larocca/Nim,xland/Nim,russpowers/Nim,kirbyfan64/Nim,jsanjuas/Nim,gokr/Nim,jsanjuas/Nim,mbaulch/Nim,tmm1/Nim,Salafit/Nim,JCavallo/Nim,endragor/Nim,Matt14916/Nim,xland/Nim,Matt14916/Nim,nimLuckyBull/Nim,MrJohz/Nim,judofyr/Nim,judofyr/Nim,msmith491/Nim,mbaulch/Nim,douglas-larocca/Nim,jfhg/Nim,Senketsu/Nim,xland/Nim,tmm1/Nim,dom96/Nim,fredericksilva/Nim,tulayang/Nim,kirbyfan64/Nim,singularperturbation/Nim,sarvex/Nim-lang,nafsaka/Nim,reactormonk/nim,haiodo/Nim,msmith491/Nim,kirbyfan64/Nim,greyanubis/Nim,jsanjuas/Nim,jsanjuas/Nim,judofyr/Nim,gokr/Nim,xland/Nim,greyanubis/Nim,nimLuckyBull/Nim,sferik/Nim,fredericksilva/Nim,reactormonk/nim,bvssvni/Nim,dom96/Nim,MrJohz/Nim,Matt14916/Nim,jsanjuas/Nim,nafsaka/Nim,kirbyfan64/Nim,tulayang/Nim,nanoant/Nim,sarvex/Nim-lang,nimLuckyBull/Nim,douglas-larocca/Nim,judofyr/Nim,russpowers/Nim,dom96/Nim,msmith491/Nim,msmith491/Nim,zachaysan/Nim,mbaulch/Nim,Senketsu/Nim,Dhertz/Nim,greyanubis/Nim,sferik/Nim,zachaysan/Nim,fmamud/Nim,fmamud/Nim,jfhg/Nim,fmamud/Nim,reactormonk/nim,bvssvni/Nim,endragor/Nim,endragor/Nim,nafsaka/Nim,sarvex/Nim-lang,russpowers/Nim,xland/Nim,sarvex/Nim-lang,MrJohz/Nim,nafsaka/Nim,JCavallo/Nim,JCavallo/Nim,greyanubis/Nim,endragor/Nim,Matt14916/Nim,gokr/Nim,Matt14916/Nim,Dhertz/Nim,BlaXpirit/nim,nanoant/Nim,MrJohz/Nim,dom96/Nim,tulayang/Nim,bvssvni/Nim,greyanubis/Nim,mbaulch/Nim,tulayang/Nim,sferik/Nim,douglas-larocca/Nim,Salafit/Nim,BlaXpirit/nim,dom96/Nim,singularperturbation/Nim,msmith491/Nim,fmamud/Nim,gokr/Nim,haiodo/Nim,endragor/Nim,Senketsu/Nim,douglas-larocca/Nim,jfhg/Nim,reactormonk/nim,reactormonk/nim,fredericksilva/Nim,gokr/Nim,sferik/Nim,gokr/Nim,bvssvni/Nim,reactormonk/nim,russpowers/Nim,tulayang/Nim,Senketsu/Nim,bvssvni/Nim,reactormonk/nim,sferik/Nim,jsanjuas/Nim,nimLuckyBull/Nim,fredericksilva/Nim,gokr/Nim,nafsaka/Nim,Dhertz/Nim,tmm1/Nim,nanoant/Nim,singularperturbation/Nim,bvssvni/Nim,nafsaka/Nim,MrJohz/Nim,nanoant/Nim,zachaysan/Nim,BlaXpirit/nim,Salafit/Nim,JCavallo/Nim,nimLuckyBull/Nim,douglas-larocca/Nim,mbaulch/Nim,tmm1/Nim,sferik/Nim,fmamud/Nim,Senketsu/Nim,fmamud/Nim,Salafit/Nim,haiodo/Nim,mbaulch/Nim,nafsaka/Nim,gokr/Nim,zachaysan/Nim,sarvex/Nim-lang,jfhg/Nim,JCavallo/Nim,xland/Nim,reactormonk/nim,fredericksilva/Nim,BlaXpirit/nim,judofyr/Nim,sarvex/Nim-lang,Salafit/Nim,Salafit/Nim,endragor/Nim,JCavallo/Nim,tulayang/Nim,russpowers/Nim,kirbyfan64/Nim,tmm1/Nim,BlaXpirit/nim,singularperturbation/Nim,fmamud/Nim,Salafit/Nim,tmm1/Nim,zachaysan/Nim,dom96/Nim,Dhertz/Nim,douglas-larocca/Nim,jfhg/Nim,zachaysan/Nim,greyanubis/Nim,fredericksilva/Nim,jfhg/Nim,Senketsu/Nim,BlaXpirit/nim,BlaXpirit/nim,zachaysan/Nim,Matt14916/Nim,Dhertz/Nim,kirbyfan64/Nim,judofyr/Nim,MrJohz/Nim,nanoant/Nim,judofyr/Nim,nimLuckyBull/Nim,tmm1/Nim,jsanjuas/Nim,douglas-larocca/Nim,bvssvni/Nim,msmith491/Nim,xland/Nim