How to limit the script to check if Table is not empty and run it each time it's changed?

So, I'm trying to make a brick whom will give admin commands to people who touch it. I have this so far:

Admin = {}

script.Parent.Touched:connect(function(hit)
if hit.Parent:findFirstChild("Humanoid") then
Admin[hit.Parent.Name]=game.Players:GetPlayerFromCharacter(hit.Parent)
end
end)

for i=1,#Admin do 
if game.Players:FindFirstChild(Admin[i]) ~= nil then 
A=game.Players:FindFirstChild(Admin[i]) 
end 
end 
A.Chatted:connect(function(msg)
	if string.sub(msg,1,5) == "give;"  then 
		p = Game:GetService("InsertService"):loadAsset(string.sub(msg,6)) 
		p.Parent = Game.Workspace 
		p:MakeJoints() 
		p:MoveTo(game.Workspace.Admin[i].Torso.Position)
end
end)

Output: 21:48:02.545 - Workspace.Acquire "give;" Commands.Head.Script:14: attempt to index global 'A' (a nil value)

So, I'm wondering, how do you make it work and not break since the Admins list is empty at the first but the script runs immediately and breaks.. Any clues how to fix it?

Thanks!

A working and more efficient way of doing this is connecting the Chatted event inside the Touched event.

Admin = {}

script.Parent.Touched:connect(function(hit)
	if game.Players:GetPlayerFromCharacter(hit.Parent) then -- using GetPlayerFromCharacter will detect if it's a player that touched the brick, not just anything with a Humanoid in it.
		local player = game.Players:GetPlayerFromCharacter(hit.Parent)
		if not pcall(function() return Admin[player.Name] end) then
			Admin[player.Name] = player
			
			player.Chatted:connect(function(msg)
				if string.sub(msg,1,5) == "give;" then
			        	p = Game:GetService("InsertService"):LoadAsset(string.sub(msg,6)) 
			        	p.Parent = Game.Workspace 
				        p:MakeJoints() 
				        p:MoveTo(player.Character.Torso.Position)
		    		end
			end)
		end
	end
end)