Bug/Improvement: Add additional error messaging if user does not select a metro or a state in calculator

[m3ssij3ssi]

Steps to replicate - on the Apartment Calculator Page https://weareapartments.org/calculator

1. Check "Potential new development"
2. Put in 100 (or any number) for number of homes
3. Check "Metro" OR "State. But do not select a metro
4. Website returns blank page.

Can we either

1. Return an error message and say "please select a state" and "please select a metro" if no selection was made?

2. OR have the same behavior as the live production site - where if someone forgets to enter a metro or state, the site just returns national numbers.

Option 1 is preferable as it would make the most sense to users but let me know.

this can be done after July 12 if you need more time on this.