fix(Runtime): DeformationJob checks for animator avatar for bone queries

Summary: Animator's `GetBoneTransform` used to simply return null if the Animator's avatar component was set to null (https://docs.unity3d.com/2021.1/Documentation/ScriptReference/Animator.GetBoneTransform.html). In later versions (https://docs.unity3d.com/ScriptReference/Animator.GetBoneTransform.html), an exception is thrown. To prevent that, bone queries should make sure that the avatar component is not null.

Reviewed By: mvaganov-fb

Differential Revision: D52575669

fbshipit-source-id: c0fb9521ef8b1704f2fddf14c3e27b9fd474f33f

Author: sohailshafiiWk

Runtime/Scripts/AnimationRigging/DeformationJob.cs

@@ -700,9 +700,11 @@ public override DeformationJob Create(Animator animator, ref T data, Component c
             job.RightLowerArmToHandAxis = data.RightArm.LowerArmToHandAxis;
             job.HipsIndex = (int)HumanBodyBones.Hips;
             job.SpineLowerIndex = job.HipsIndex + 1;
-            job.SpineUpperIndex = animator.GetBoneTransform(HumanBodyBones.Chest) != null ?
+            job.SpineUpperIndex =
+                (animator.avatar != null && animator.GetBoneTransform(HumanBodyBones.Chest) != null) ?
                 job.SpineLowerIndex + 1 : -1;
-            job.ChestIndex = animator.GetBoneTransform(HumanBodyBones.UpperChest) != null ?
+            job.ChestIndex =
+                (animator.avatar != null && animator.GetBoneTransform(HumanBodyBones.UpperChest) != null) ?
                 job.SpineUpperIndex + 1 : -1;
             job.HeadIndex = data.HipsToHeadBones.Length - 1;