Dia crashes when applying/saving preferences

["Phillip Neiswanger" <sigsegv0 gmail com>]

Hi,

While working on the zoom patch Dia has crashed on me several times. I'm  
not really sure I should report it since Dia is still being developed.  
Basically, preferences are unusable. It crashes in prefs_set_length_unit()  
because the parameter is null. Not sure if this is an issue, but there is  
a call in preferences.c to update_internal_prefs() which is passed null  
arguments. I can't image that would work given the code.

If you need more, let me know.
--
phil