The Problem

I'm automating my X11 desktop and watch for windows with certain titles. But sometimes X11::GUITest doesn't find a given window anymore and then xlib takes the complete Perl process with it because X11::GUITest doesn't install the appropriate error handler for missing windows or windows without window decoration.

Error message:

X Error of failed request:  BadWindow (invalid Window parameter)
  Major opcode of failed request:  15 (X_QueryTree)
  Resource id in failed request:  0x0
  Serial number of failed request:  22767
  Current serial number in output stream:  22767

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