Add missing command col exists check

Author: Kissaki

needs-update/custom-completions/auto-generate/parse-fish.nu

@@ -104,6 +104,7 @@ def cleanup_subcommands [] {
 def make-commands-completion [] {
     let fishes = $in
     $fishes
+    | where ('command' in ($fishes | columns))
     | get command
     | uniq         # command is cloned on every complete line
     | each { |command|