User is able to add empty hashtags while customizing newsfeed.

Summary

(Summarize the bug encountered concisely)

Steps to reproduce

1. In Discovery, click on #HASHTAGS drop down and select MORE.
2. Don't type anything.
3. Press ✔ next to the input.

Platform information

HUAWEI (HUAWEI ANE-LX1) / Android 8.0.0

Environment: Huawei P20 lite, Android 8, Chrome browser

What is the current bug behavior?

User is able to add as many empty hashtags as she/he wants.

What is the expected correct behavior?

Empty hashtags should not be allowed

Relevant logs and/or screenshots

https://dashboard.ubertesters.com/uploads/8463/11810/issues/10/151643/clear%20hashtag.mp4

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)