I have a treegrid which is working fine.  Now I need to click (or double click) on a row to popup a form.  When I add

onClickRow: function(row) { alert('hello world'); },

I get the following in the JS console

[Error] TypeError: null is not an object (evaluating 'row[field]')
   clickEventHandler (jquery.easyui.all.js:13755)
   clickEventHandler (jquery.easyui.all.js:16788)
   dispatch (jquery-3.2.1.min.js:3:10322)

Any ideas?

Jim