Check for node before using it

npm-run-completion.zsh

@@ -7,7 +7,7 @@ _npm_run_completion() {
         break
       fi
   done
-  if [ ! "$dir" = "" ]; then
+  if [ ! "$dir" = "" ] && type node > /dev/null; then
     local options=("${(@f)$(node -e "var pkg = require('$dir/$filename'); pkg.scripts && Object.keys(pkg.scripts).forEach(function(script) { console.log(script.replace(':', '\\\:')+':$ '+pkg.scripts[script]) })")}")
     _describe 'values' options
   fi