RE: SalesEditLine Modification
your error message saying that you are trying to run SalesEditLine (Form) directly without calling it by passing any parameters.
Those needed parameters are being checked in init() method of form and are failing to get what they need
you cannot invoice order by directly opening this form.
you can try any of following
Go to all sales orders windows and select multiple order and click invoice button, if its allows you to select invoice button with multiple orders selection
or
In periodic section of Accounts Receivable you will find Sales Update >> Invoice, there you can generate mass invoices
or
write code to generate multiple invoices for sales orders