rtk.Window.onclick doesn't fire anymore

[jtackaberry]

onclick event handler is not firing for rtk.Window:

-- Set package path to find rtk installed via ReaPack
package.path = reaper.GetResourcePath() .. '/Scripts/rtk/1/?.lua'
-- Load the package
local rtk = require('rtk')
-- Set the module-local log variable for more convenient logging.  Throughout
-- this tutorial we will assume both rtk and log variables have been set.
local log = rtk.log
log.level = log.DEBUG

local window = rtk.Window{w=640, h=480}
window.onclick = function()
    log.info('clicked')
end
window:open()

See also #29