Strange output with multi width emojis

[yangm97]

Using LUA 5.1 on macOS

local utf8 = require 'utf8'

local t = {}
local str = "text 😅 👨‍💻 🇧🇷 🏳️‍🌈"
for i=1, utf8.len(str) do
	t[i]= (utf8.sub(str,i,i))
end
for k , v in pairs(t) do
	print(k,v)
end

Output:

1	t
2	e
3	x
4	t
5	 
6	😅
7	 
8	👨
9	‍
10	💻
11	 
12	🇧
13	🇷
14	 
15	🏳
16	️
17	‍
18	🌈