Fix escapeSingleQuote trying to escape undefined value

[TimAConner]

Description

Change escapeSingleQuotes to check if value being passed into it is a string or not. If it is, escape. If not, don't escape string.

Problem to Solve

Check if value trying to be escape is a string or not. If it is a string, escape it, if not, don't escape it. Before it was trying to run a .replace method on an undefined object.

Proposed Changes

Check if value to be escaped is a string or not.

Expected Behavior

No errors should be thrown when running npm run db:generate

Steps to Test Solution

1. Run npm run db:generate
2. There should be no errors. The output should be:

   > bangazon-api-sprint1@1.0.0 db:generate C:\Users\Tim\workspace\group-projects\bangazon-api-sprint1
   > node db/build-db.js