fix: 🐛 fix bash-completion sourcing error

see #67 (closed)

this PR makes the bash completion installation code more robust to resolve the error encountered after running the Ludus installer script where bash_completion.sh expects $XDG_CONFIG_HOME/bash_completion to be a file not a directory

Signed-off-by: goproslowyo 13938668-goproslowyo@users.noreply.gitlab.com