Fix build warnings about missing field initializer

[rbuj]

appearance-main.c:163:14: warning: missing field 'short_name' initializer [-Wmissing-field-initializers]
      { NULL }
             ^
--
mate-da-capplet.c:785:8: warning: missing field 'short_name' initializer [-Wmissing-field-initializers]
                {NULL}
                     ^
--
mate-keyboard-properties.c:181:8: warning: missing field 'short_name' initializer [-Wmissing-field-initializers]
                {NULL}
                     ^
--
eggcellrendererkeys.c:70:3: warning: missing field 'value_table' initializer [-Wmissing-field-initializers]
                };
                ^
--
eggcellrendererkeys.c:525:7: warning: missing field 'value_table' initializer [-Wmissing-field-initializers]
      };
      ^
--
mate-mouse-properties.c:402:8: warning: missing field 'short_name' initializer [-Wmissing-field-initializers]
                {NULL}
                     ^
--
font-thumbnailer.c:199:13: warning: missing field 'short_name' initializer [-Wmissing-field-initializers]
            { NULL }
                   ^
--
font-view.c:794:47: warning: missing field 'padding' initializer [-Wmissing-field-initializers]
    { "about", action_about, NULL, NULL, NULL },
                                              ^
font-view.c:795:45: warning: missing field 'padding' initializer [-Wmissing-field-initializers]
    { "quit", action_quit, NULL, NULL, NULL }
                                            ^
--
control-center.c:165:8: warning: missing field 'short_name' initializer [-Wmissing-field-initializers]
                {NULL}
                     ^
--
main.c:65:11: warning: missing field 'short_name' initializer [-Wmissing-field-initializers]
          { NULL }
                 ^
--
drw-monitor.c:78:3: warning: missing field 'value_table' initializer [-Wmissing-field-initializers]
                };
                ^