When you save a file, entering a name, you are given a second dialog, labelled, "Export srzip session file" with a text box labelled "Filename" The dialog is intended to show output options, but there are no options for srzip, so it shouldn't be shown. Places to look, from jhol: you need to have a look here: http://sigrok.org/gitweb/?p=pulseview.git;a=blob;f=pv/mainwindow.cpp;h=f907f09cce33f118b0c830dbc0ee564f50a76501;hb=HEAD#l239
Or possibly there are some options, but they're all of types that PV doesn't know how to handle, so it shows and empty list.
In any case, it seems weird that the filename has to be entered twice.
Fixed in http://sigrok.org/gitweb/?p=libsigrok.git;a=commit;h=37875f7506143d97f44014260f07e6408ee8c9dc and http://sigrok.org/gitweb/?p=pulseview.git;a=commit;h=ad83f8faadeded7902eb3e25b608f45674b86fa0