[#2284] Remove more compilation/execution warnings

sflphone-client-gnome/src/callable_obj.c

sflphone-client-gnome/src/conference_obj.c

sflphone-client-gnome/src/config/accountconfigdialog.c

sflphone-client-gnome/src/config/assistant.c

sflphone-client-gnome/src/config/zrtpadvanceddialog.c

sflphone-client-gnome/src/mainwindow.c

sflphone-client-gnome/src/ui.xml

sflphone-client-gnome/src/uimanager.c