completion: Only run cd if .dim-last-path exists

We currently always cat .dim-last-path and cd to whatever content it
has.

However, it's not guarantee to exists, so the initial cat might not
work. Make sure we only switch to it if the file exists in the first
place.

Suggested-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>

bash_completion

@@ -3,7 +3,11 @@
 dim ()
 {
 	if [[ "$1" = "cd" ]]; then
-		cd $(cat ~/.dim-last-path) || return 1
+		if [ -e "~/.dim-last-path" ]; then
+			cd $(cat ~/.dim-last-path) || return 1
+		else
+			return 1
+		fi
 	else
 		command dim "$@"
 	fi