B20, on NT4.0: Bash crashes when background process ends

[Robert Kieffer <kieffer at alodar dot com>]

[My apologies for not including a fix with this.  I haven't figured
out where the Bash source is located, not to mention not really having
the time.]

This is a repeatable bug.

- Launch bash.
- Start a background process that does not immediately exit (e.g. "tail -f somefile &")
- In the task manager, kill that process
- Now click the bash window
- * crash * ... The bash window goes away.

If you do the same thing with the process in the foreground (no '&' on the command line), bash does not go away.

If you look really carefully at the bash window in the milliseconds between when you click on it and when it disappears, you can see the word "exit" displayed.

My conjecture is that some process cleanup code is failing to recognize the fact that the background process has already gone away.  When you return to Bash, it tries to "clean up" the background processes by popping the most recent process "off the stack", which in this case happens to be the main Bash process.