Wasn't sure where else to put this, but the ArrayTableGetItem action was giving an error in the editor. After a little digging, I found that GetItem was adapted from SetItem but the associated inspector script wasn't updated for these changes.
Note: the side-effect of my fix is that ArrayTableGetItem has a field called 'value'. This is actually the result of the GetItem call. I mention this because value is normally something retrieved by the action rather than something returned by an action. Although the field is labelled 'value', it functions like a 'result' field. I'm sure someone smarter can tidy this up so that the field is labelled correctly.
The path for this file is "Assets\PlayMaker ArrayMaker\Addons\Custom\Table\Actions\Editor"