ginetaddressmask: plug leak

ginetaddressmask: plug leak

==24706== 52 bytes in 1 blocks are definitely lost in loss record 7,248 of 13,092
==24706==    at 0x4A074CD: malloc (vg_replace_malloc.c:236)
==24706==    by 0x70E9F5F: standard_malloc (gmem.c:85)
==24706==    by 0x70E9FE8: g_malloc (gmem.c:159)
==24706==    by 0x71018EC: g_slice_alloc (gslice.c:1003)
==24706==    by 0x710192B: g_slice_alloc0 (gslice.c:1029)
==24706==    by 0x7068526: g_type_create_instance (gtype.c:1872)
==24706==    by 0x705067B: g_object_constructor (gobject.c:1835)
==24706==    by 0x704FE47: g_object_newv (gobject.c:1699)
==24706==    by 0x7050612: g_object_new_valist (gobject.c:1816)
==24706==    by 0x704F894: g_object_new (gobject.c:1531)
==24706==    by 0x6F0F2F0: g_inet_address_new_from_bytes (ginetaddress.c:459)
==24706==    by 0x6F5D703: remove_network (gnetworkmonitornetlink.c:256)
==24706==    by 0x6F5DD80: read_netlink_messages (gnetworkmonitornetlink.c:386)
==24706==    by 0x6F2D5CA: socket_source_dispatch (gsocket.c:2505)
==24706==    by 0x70E1D45: g_main_dispatch (gmain.c:2513)
==24706==    by 0x70E2A06: g_main_context_dispatch (gmain.c:3050)
==24706==    by 0x70E2BE9: g_main_context_iterate (gmain.c:3121)
==24706==    by 0x70E2CAD: g_main_context_iteration (gmain.c:3182)
==24706==    by 0x6F60A05: g_application_run (gapplication.c:1599)
==24706==    by 0x42D011: main (ephy-main.c:472)

https://bugzilla.gnome.org/show_bug.cgi?id=667098