When a FileChooser is included in a simulation and the later is used as an applet a security exception is raised and the applet fails.
This is fine, but unfortunately it also happens when _isApplet() is used to make sure FileChooser is only used when the simulation is not run as a standalone program, as in the enclosed simulation.
Is there any workaround to allow the same source to generate simulations to be run standalone and as an applet?
This was an unexpected behavior... (ok, a bug! :-) ) because I didn't foresee this possibility.
I have changed the FileChooser model element so that, if the simulation cannot access the disk, the filechooser will display an error dialog and return null if you try to select a file. But your simulation won't crash.
Notice that checking for _isApplet() may be misleading, since a signed applet could actually access the disk. (But maybe you want to forbid also this possibility, in which case using :isApplet(9 would be correct, of course).
I have uploaded a new EJS version that is still beta, but you can work with it to polish your simulation. The new release, soon to come, will have this code ready.
The new EJS is at http://fem.um.es/EjsWiki/uploads/Download/EJS_4.3.5_111129.zip