Interviews - When leaving blank on initial job entry, it should not make a POST request

**Describe the bug**
When going through adding a job, the final step is to add interview notes (if you've had one). The form says you can leave it blank if you haven't. However if you do leave it blank the client still makes a POST request to the interviews route and recieves a 422 error.

**To Reproduce**
Steps to reproduce the behavior:
1. Login
2. Add Job
3. Fill out info on first 2 forms
4. Leave interviews form blank and click finish + save
5. Look at Dev Tools

**Expected behavior**
I would expect the client not to make the POST request if the interview form is left blank by the user

**Screenshots**

**Desktop (please complete the following information):**
- OS: [e.g. iOS]
- Browser [e.g. chrome, safari]
- Version [e.g. 22]

**Smartphone (please complete the following information):**
- Device: [e.g. iPhone6]
- OS: [e.g. iOS8.1]
- Browser [e.g. stock browser, safari]
- Version [e.g. 22]

**Additional context**
NOTE: This probably doesn't need to be fixed for MVP

Reproduce the add-job flow by completing the first two forms, leaving interview notes blank, and watching Dev Tools for the POST to the interviews route. Trace the client request from the final save step; done means no interview POST is sent for a blank form and the job saves without a 422 response.

Written by the indexing model from the issue text.