escript: exception error: no function clause matching 'keynote-to-text':slide_id("key:master-slide-0")

[hnsl]

I would love to be able to diff my presentation properly to keep track of changes. I use Keynote 6 but you can export your presentation in Keynote 09' format so I did and got the following crash:

escript: exception error: no function clause matching
'keynote-to-text':slide_id("key:master-slide-0") (src/keynote-to-text.erl, line 96)
in function 'keynote-to-text':'-slides/1-fun-0-'/2 (src/keynote-to-text.erl, line 45)
in call from erlsom_sax_utf8:wrapCallback/2 (src/erlsom_sax_utf8.erl, line 1364)
in call from erlsom_sax_utf8:parseContentLT/2 (src/erlsom_sax_utf8.erl, line 922)
in call from erlsom_sax_utf8:parse/2 (src/erlsom_sax_utf8.erl, line 196)
in call from 'keynote-to-text':slides/1 (src/keynote-to-text.erl, line 64)
in call from 'keynote-to-text':main/1 (src/keynote-to-text.erl, line 13)