New Array, not exactly empty

I have a habit of creating powershell scripts that iniitialize an empty array such as

$a=@()

which I than can use later to add items to it with

$a += $something

Normally for what I do with it, that's fine, but recently I wanted to do a check at the end of the script to see if there were any results:

 if ($a.count -gt 0) {  }

expecting this to be false if nothing was added to the array.  But my script was failing unexpectedly as it seems there is a $null value put in the first position of the array.  So a better way to evaluate in my case is:

if ($a[0] -ne $null) {  }