title: Unity AddComponent return null
body: <p>I have a Monobehavior with or without a Rigidbody2D component. I want to get it or create it if needed.</p>
  
  <p>The <strong>AddComponent</strong>, returns null on my game. Often, not every time,
  the log appeared.</p>
  
  <p>Using:</p>
  
  <ul>
  <li>Unity 2019.2.19</li>
  <li>Android Platform</li>
  </ul>
  
  <pre class="lang-cs prettyprint-override"><code>void Start()
  {
      Rigidbody2D rb = gameObject.GetComponent&lt;Rigidbody2D&gt;() ?? 
          gameObject.AddComponent&lt;Rigidbody2D&gt;();
  
      if (rb == null)
      {
          Debug.LogError("No way to be here!");
      }
  }
  </code></pre>
  
  <p>I can remove the ?? and do this in multiple lines, it doesn't change the error.</p>
  
  <p>Do you have a solution to get the Rigidbody2D component?</p>