[unity] URP shader build error when added to always included shaders. Closes #2406.

spine-unity/Modules/com.esotericsoftware.spine.urp-shaders/Shaders/2D/Spine-Skeleton-URP-2D.shader

@@ -64,5 +64,5 @@ Shader "Universal Render Pipeline/2D/Spine/Skeleton" {
 		}
 	}
 
-	FallBack "Hidden/InternalErrorShader"
+	FallBack "Universal Render Pipeline/2D/Sprite-Unlit-Default"
 }

spine-unity/Modules/com.esotericsoftware.spine.urp-shaders/Shaders/2D/Spine-SkeletonLit-URP-2D.shader

@@ -244,5 +244,5 @@ Shader "Universal Render Pipeline/2D/Spine/Skeleton Lit" {
 			ENDHLSL
 		}
 	}
-	FallBack "Universal Render Pipeline/2D/Sprite-Lit-Default"
+	FallBack "Universal Render Pipeline/2D/Spine/Skeleton"
 }

spine-unity/Modules/com.esotericsoftware.spine.urp-shaders/Shaders/Outline/Spine-Skeleton-OutlineOnly-URP.shader

@@ -56,6 +56,5 @@ Shader "Universal Render Pipeline/Spine/Outline/Skeleton-OutlineOnly" {
 		}
 	}
 
-	FallBack "Hidden/InternalErrorShader"
 	CustomEditor "SpineShaderWithOutlineGUI"
 }

spine-unity/Modules/com.esotericsoftware.spine.urp-shaders/Shaders/Spine-Skeleton-URP.shader

@@ -139,5 +139,5 @@ Shader "Universal Render Pipeline/Spine/Skeleton" {
 		}
 	}
 
-	FallBack "Hidden/InternalErrorShader"
+	FallBack "Universal Render Pipeline/Unlit"
 }

spine-unity/Modules/com.esotericsoftware.spine.urp-shaders/Shaders/Spine-SkeletonLit-URP.shader

@@ -194,5 +194,5 @@ Shader "Universal Render Pipeline/Spine/Skeleton Lit" {
 		}
 	}
 
-	FallBack "Hidden/InternalErrorShader"
+	FallBack "Universal Render Pipeline/Spine/Skeleton"
 }

spine-unity/Modules/com.esotericsoftware.spine.urp-shaders/Shaders/Spine-Sprite-URP.shader

@@ -276,6 +276,6 @@ Shader "Universal Render Pipeline/Spine/Sprite"
 		}
 	}
 
-	FallBack "Hidden/InternalErrorShader"
+	FallBack "Universal Render Pipeline/Spine/Skeleton"
 	CustomEditor "SpineSpriteShaderGUI"
 }

spine-unity/Modules/com.esotericsoftware.spine.urp-shaders/package.json

@@ -2,7 +2,7 @@
   "name": "com.esotericsoftware.spine.urp-shaders",
   "displayName": "Spine Universal RP Shaders",
   "description": "This plugin provides universal render pipeline (URP) shaders for the spine-unity runtime.\n\nPrerequisites:\nIt requires a working installation of the spine-unity runtime, version 4.1.\n(See http://esotericsoftware.com/git/spine-runtimes/spine-unity)",
-  "version": "4.1.26",
+  "version": "4.1.27",
   "unity": "2019.3",
   "author": {
     "name": "Esoteric Software",