title: Eslint nullish coalescing combined with optional chaining problem
body: <p>Lets say we have these three expressions linted by eslint:</p>
  
  <pre><code>const exp1 = a ?? b; // ok
  const exp2 = a?.b // ok
  const exp3 = a?.b ?? c // Parsing error: ':' expected.
  </code></pre>
  
  <p>All works and are successfully compiled with typescript, but the last expression throws eslint error <code>Parsing error: ':' expected.</code> It seems there is problem with combination of Nullish coalescing and optional chaining. Is there someone who met this problem?</p>
  
  <p>package.json</p>
  
  <pre><code>"eslint": "5.16.0",
  "eslint-config-airbnb-base": "13.1.0",
  "eslint-plugin-import": "2.17.2",
  "ts-node": "8.5.4",
  "typescript": "3.7.4"
  </code></pre>