Array offset is not being applied to unions

```ts
declare function foo(): [string, string] | [number, number];
let a = foo();
let b = a[0];

declare function bar(): string[] | number[];
let c = bar();
let d = c[0];
```
```lua
local a = foo();
local b = a[0]; --Needs +1

local c = bar();
local d = c[0]; --Needs +1
```
