The program 'leafpad' received an X Window System error.
This probably reflects a bug in the program. The error was 'BadWindow (invalid Window parameter)'. (Details: serial 15113 error_code 3 request_code 18 minor_code 0) (Note to programmers: normally, X errors are reported asynchronously; that is, you will receive the error a while after causing it. To debug your program, run it with the --sync command line option to change this behavior. You can then get a meaningful backtrace from your debugger if you break on the gdk_x_error() function.)
I'm sorry I missed the Issue.
It seems to be happening in other software, but I couldn't find the code to solve it. https://www.google.com/search?q=%22BadWindow+(invalid+Window+parameter)%22+%22error_code+3+request_code+18+minor_code+0%22
I would appreciate if someone could give me some information about the code to solve this problem.