add safety check to avoid infinite cat hang

borgmatic/commands/completion.py

@@ -161,6 +161,7 @@ def fish_completion():
             function __borgmatic_check_version
                 set -fx this_filename (status current-filename)
                 fish -c '
+                    if test -f "$this_filename"
                         set this_script (cat $this_filename 2> /dev/null)
                         set installed_script (borgmatic --fish-completion 2> /dev/null)
                         if [ "$this_script" != "$installed_script" ] && [ "$installed_script" != "" ]
@@ -170,6 +171,7 @@ def fish_completion():
                             '$this_filename',
                         )}"
                         end
+                    end
                 ' &
             end
             __borgmatic_check_version