fix: defensive check on accessing cmd.args

Author: remy

lib/monitor/run.js

@@ -86,7 +86,7 @@ function run(options) {
   if (
     // this is a hack to avoid forking if there's a node argument being passed
     // it's a short term fix, and I'm not 100% sure that `fork` is the right way
-    cmd.args[0].indexOf('-') === -1 &&
+    (cmd.args[0] || '').indexOf('-') === -1 &&
     executable === 'node' &&
     utils.version.major > 4
   ) {