assertion `GTK_IS_PROGRESS_BAR (pbar)' failed when closing the window while the progress bar is pulsing

[Colossus <colossus 3000 it>]

Hi,

It appears in my app that when a progress bar is pulsing and I close 
the window by clicking on the X upper right button I receive the 
message in the subject. If I wait for the progress bar to finish 
pulsing I don't get the warning. Why this ?
--
Colossus
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