Getting error in dhtmlxgrid.js

hi,

‘this.rowsCol[…]._cntr’ is null or not an object dhtmlxgrid.js, line 95 character 153
‘this.selectedRows[…].idd’ is null or not an object dhtmlxgrid.js, line 136 character 125

and after this error came context menu doesn’t appear

-n’s

Can you provide steps, how to recreate such problems?