I understood the problem.
It is mandatory to give a value to “editurl”, even if there is no extern source of data and only an array, and event if the file provided to “editurl” is empty! What is rather surprising.

In looking at the content of functions editRow and saveRow. I think it would be easy to avoid that. When I will have time I would suggest perhaps change in “grid.inlinedit.js”, that will avoid the call to “$. ajax”, based for example on
“$t.p.data”.

But perhaps you have already tried and that is a problem?
Best regards