Using umlaute in function names breaks the .hex

[joernalraun]

You can make use of Umlaute (such as ö, ä, ü, or even ß) in function names. When saving a hex file from this and trying to open it, the browser window becomes unresponsive after a while. All changes (before it doesn't react anymore) are not saved to the file.

It would be good if certain letters could not be used (and/or a message appears when using them) in such instances.