LayeredBlendPerBone with BlendRootMotionBasedOnRootBone set incorrectly calculates root motion weightings with more than two sources

for (int32 ChildIndex = 0; ChildIndex < BlendPoses.Num(); ++ChildIndex)
{
    const float ChildWeight = BlendWeights[ChildIndex];
    if (FAnimWeight::IsRelevant(ChildWeight))
    {
       if (bHasRelevantPoses == false)
       {
          // Update cached data now we know we might be valid
          UpdateCachedBoneData(Context.AnimInstanceProxy->GetRequiredBones(), Context.AnimInstanceProxy->GetSkeleton());

          // Update weights
          FAnimationRuntime::UpdateDesiredBoneWeight(DesiredBoneBlendWeights, CurrentBoneBlendWeights, BlendWeights);
          bHasRelevantPoses = true;

          if(bBlendRootMotionBasedOnRootBone && !CurrentBoneBlendWeights.IsEmpty())
          {
             const float NewRootMotionWeight = CurrentBoneBlendWeights[0].BlendWeight;
             if(NewRootMotionWeight > ZERO_ANIMWEIGHT_THRESH)
             {
                RootMotionWeight = NewRootMotionWeight;
                RootMotionBlendPose = CurrentBoneBlendWeights[0].SourceIndex;
             }
          }
       }

       const float ThisPoseRootMotionWeight = (ChildIndex == RootMotionBlendPose) ? RootMotionWeight : RootMotionClearWeight;
       BlendPoses[ChildIndex].Update(Context.FractionalWeightAndRootMotion(ChildWeight, ThisPoseRootMotionWeight));
    }
}