fix(lua): always return nil values in vim.tbl_get when no results

While `return` and `return nil` are for most intents and purposes
identical, there are situations where they're not. For example,
calculating the amount of values via the `select()` function will yield
varying results:

```lua
local function nothing() return     end
local function null()    return nil end

select('#', nothing()) -- 0
select('#', null())    -- 1
```

`vim.tbl_get` currently returns both nil and no results, which makes it
unreliable to use in certain situations without manually accounting for
these discrepancies.

0 files changed, 0 insertions, 0 deletions