I found out the issue. Just one note that the error message is not correct (at least, for me). I think it happens like this:
I commit one object. Then, It triggers some js actions. One of them is not succeeded because it tries to access "x" of null.
However, somewhere else, Mendix tries to call action "retrievebyids" with the ID of object I just commit (for the Mx Datagrid widget, I think), and receives the correct response.
In the callback function of "retrievebyids", it sees the error ('x' of null) and just add it as error of callback of "retrievebyids"?
Anyway, it is over now :) Thanks,
mxui.js is in your mendix runtime directory. You can make it readable with notepad++ just for debugging reasons, but probably your widget is incorrect and passing something empty ('of null')
it seems that that file is not "design for human". The reason I want to look into that file is because:
When I execute one js event, it fires a lot of events which register to a listener that associates with that event. One of them goes wrong and immediately it jumps to mxui.js and ends at get.mx.server.request.options.callback. I guest that this is caused by Dojo deferred action. But I dont know why.
I will check elsewhere!
Looking at the error message, an unhandled error occurs in the callback handler you passed to mx.data.get. Because this error is not handled in the callback function, mx.data.get throws an generic error message, along with the error description. You could add a try/catch to the callback function to find out where the error occurs. Apparently you are trying to read the 'x' property of an empty reference.