[unity] Fixed a bug in SpineMecanim which caused dipping to SetupPose during transitions due to MixBlend.Replace on first track.

spine-unity/Assets/Spine/Runtime/spine-unity/Components/SkeletonMecanim.cs

@@ -367,7 +367,7 @@ namespace Spine.Unity {
 				for (int layer = 0, n = animator.layerCount; layer < n; ++layer) {
 					var controller = animator.runtimeAnimatorController as UnityEditor.Animations.AnimatorController;
 					if (controller != null) {
-						layerBlendModes[layer] = MixBlend.Replace;
+						layerBlendModes[layer] = MixBlend.First;
 						if (layer > 0) {
 							layerBlendModes[layer] = controller.layers[layer].blendingMode == UnityEditor.Animations.AnimatorLayerBlendingMode.Additive ?
 								MixBlend.Add : MixBlend.Replace;