pidgin/pidgin

Fix a bug where we tell the preferences to disconnect the wrong signals

Testing Done:
Compiled and ran, didn't seen any issues, but then again we didn't see issues before either, but this was clearly wrong.

Reviewed at https://reviews.imfreedom.org/r/184/
nullclient = executable('nullclient', 'nullclient.c', 'defines.h',
c_args : ['-DSTANDALONE'],
dependencies : [libpurple_dep, glib])