gdk: fix gtk app startup with 'g_value_set_boxed: assertion...
gdk: fix gtk app startup with 'g_value_set_boxed: assertion G_VALUE_HOLDS_BOXED (value) failed error message' when xsettings use 'XSETTINGS_TYPE_COLOR' type
gdk: fix gtk app startup with 'g_value_set_boxed: assertion G_VALUE_HOLDS_BOXED (value) failed error message' when xsettings use 'XSETTINGS_TYPE_COLOR' type