Error:Uncaught TypeError: Cannot set properties of null (setting 'innerHTML') at (index):170:25

Question

I am trying to make a js function called _ so every time I need to type getElementById I can just put _ instead. I am trying to test it out, so I want to print "this is some data". On the console in developer tools it has this error:

Uncaught TypeError: Cannot set properties of null (setting 'innerHTML')
    at (index):170:25

Here is my javascript code:

function _(element){
    return document.getElementById(element);
}

var inner_pannel = _("inner_left_pannel");

inner_pannel.innerHTML = "this is some data";

Here is some html so you understand what inner_left_pannel is.

<div id="inner_left_pannel">
                        
</div>