Handle another edge case in $PROMPT_COMMAND. #154
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In particular: bash-preexec installs itself by appending __bp_install_string to $PROMPT_COMMAND. That means that there's a pretty good change that __bp_install_string will be the last thing in $PROMPT_COMMAND when __bp_install is invoked.
If that happens, the $existing_prompt_command logic in __bp_install will result in the pre-existing prompt command followed by
:and no trailing newline. That situation is not cleaned up by the two existing special cases.Fix #153