added a fallback default to stop flow complaining

Author: KarateCowboy

src/mixins/duration.js

@@ -47,7 +47,8 @@ export default class Duration {
   async sleep (ms: number) { return new Promise(resolve => setTimeout(resolve, ms)) }
 
   async wait () {
-    let resolved = await this.sleep(this.parse(this.cmd.flags.duration))
+    let ms = this.parse(this.cmd.flags.duration) || 5000
+    let resolved = await this.sleep(ms)
     console.log('operation did not complete in provided duration')
     return resolved
   }