I was going through the rules and I came across this in the ground combat section:
It is always a good idea to carry a melee weapon, though it is not required, in the event that the enemy gets into close range (The same square) as Ranged Weapons will not be useable at that range."
So if I have my Relby's with range 0-4 if there is a enemy in the zero range(same square) that it wont work and I need a Vibroblade or something?
No, that's incorrect. You can use projectile weapons at range 0. You should report this in the Rules Updates forum in the Message Centre so someone with access can fix it, and include a link to the page you found it on.
Many of the rules were written long before anything was coded, so inaccuracies like that come up from time to time.