"[RequireComponent(typeof(UnityEngine.AI.NavMeshAgent))]" in the script throws an error to Console when attaching Game Object.
It fails to create a NavMeshAgent Component.

Steps to reproduce:
1. Open attached project "5.5"
2. Attach script Add.cs to any Game Object

Result: script fails to attach NavMeshAgent and returns an error in the Console: Assert.IsNotNull (GetComponent<UnityEngine.AI.NavMeshAgent> (), "NavMeshAgent doesn't attached!!");

Reproduced with: 5.6.0a6, 5.5.0f2
Not reproduced with: 5.4.3p2, 5.3.7p2