[unity] Fixed exception when separation leads to empty mesh with no material at SkeletonGraphic. Closes #2364.

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

@@ -842,6 +842,11 @@ namespace Spine.Unity {
 				SubmeshInstruction submeshInstructionItem = currentInstructions.submeshInstructions.Items[i];
 				Material submeshMaterial = submeshInstructionItem.material;
 				if (useOriginalTextureAndMaterial) {
+					if (submeshMaterial == null) {
+						usedMaterialItems[i] = null;
+						usedTextureItems[i] = null;
+						continue;
+					}
 					usedTextureItems[i] = submeshMaterial.mainTexture;
 					if (!hasBlendModeMaterials) {
 						usedMaterialItems[i] = this.materialForRendering;

spine-unity/Assets/Spine/package.json

@@ -2,7 +2,7 @@
 	"name": "com.esotericsoftware.spine.spine-unity",
 	"displayName": "spine-unity Runtime",
 	"description": "This plugin provides the spine-unity runtime core.",
-	"version": "4.1.23",
+	"version": "4.1.24",
 	"unity": "2018.3",
 	"author": {
 		"name": "Esoteric Software",