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/
libpurple/data/purple-url-handler.desktop.in
libpurple/protocols/null/nullprpl.c
pidgin/data/im.pidgin.Pidgin.desktop.in
sub/libpurple/data/purple-url-handler.desktop.in
sub/libpurple/protocols/null/nullprpl.c
sub/pidgin/data/im.pidgin.Pidgin.desktop.in