R-gwidgets- warning message -

i'm using package gwidgetsrgtk2 create gui can manipulate df. never worked package before i'm not expert. when try make window using gwindow works fine

gwindow("test") guiwidget of type: gwindowrgtk toolkit: guiwidgetstoolkitrgtk2 

but when try make function , asign gwindow() (or glabel, gbutton, etc.) variable win, following warning message:

win=gwindow()
warning in str.default(val) : 'str.default': 'le' na, taken 0
warning in str.default(obj, ...) :
str.default': 'le' na, taken 0

when try corresponding selected value using svalue(), following error:

error: attempt call 'gettext' on invalid reference 'obj@widget'

i have no idea how solve problem , appreciated.