Comment 2 for bug 744798

StacktraceTop:
 unit_convert_from (unit=0x0, x=0x7fffe2ed7a50, z=0x7fffe2ed3b80) at unit.c:136
 unit_category_convert (category=<value optimized out>, x=<value optimized out>, x_units=<value optimized out>, z_units=0xfff700, z=0x7fffe2ed5b00) at unit-category.c:100
 update_result_label (converter=0xf66130) at math-converter.c:72
 to_combobox_changed_cb (combo=<value optimized out>, converter=0xf66130) at math-converter.c:302
 g_closure_invoke (closure=0x1001480, return_value=0x0, n_param_values=1, param_values=0x1187380, invocation_hint=0x7fffe2ed9b70) at /build/buildd/glib2.0-2.28.4/./gobject/gclosure.c:767