I have just tried again today, and I got the following error now:

25-Aug-2016 11:20:20 | FATAL | wfu_pickatlas.m | MException thrown. Stack follows:
25-Aug-2016 11:20:20 | FATAL | mat2file | Line 0016: mat2file.c not compiled - see Makefile
25-Aug-2016 11:20:20 | FATAL | subfun | Line 0132
25-Aug-2016 11:20:20 | FATAL | subsasgn | Line 0070
25-Aug-2016 11:20:20 | FATAL | spm_write_plane | Line 0033
25-Aug-2016 11:20:20 | FATAL | spm_write_vol | Line 0083
25-Aug-2016 11:20:20 | FATAL | SaveMask | Line 2216
25-Aug-2016 11:20:20 | FATAL | cmdSaveMask_Callback | Line 1000
25-Aug-2016 11:20:20 | FATAL | wfu_pickatlas | Line 0110
25-Aug-2016 11:20:20 | FATAL | @(hObject,eventdata)wfu_pickatlas('cmdSaveMask_Callback',hObject,eventdata,guidata(hObject)) | Line 0000