Use a -debug version or use -static-rsls so the error has line numbers.
A perfect example of why anonymous functions are the devil.
Chances are you have something that is not defined in the scope of your anonymous function. I strongly suggest avoiding anonymous functions for anything requiring more than one line of code. It will make it more readable, and easier to debug.
*edit: removed possibly incorrect info*
It's looks like somethink about modal window...the popup is being clocked:
impl.addPopUp(window, parent, modal, childList, moduleFactory);
createModalWindow(parent, o, children, visibleFlag, smp, smp.getSandboxRoot());
PopUpManager.addPopUp(alert, parent, modal);
line 136 from custom as class file:
Alert.show("There was an error adding the data :(");
Any more pointers? Thanks for helping.