MeshToonMaterial: Fix clipping planes.

src/renderers/shaders/ShaderChunk/clipping_planes_pars_fragment.glsl.js

@@ -1,7 +1,7 @@
 export default /* glsl */`
 #if NUM_CLIPPING_PLANES > 0
 
-	#if ! defined( STANDARD ) && ! defined( PHONG ) && ! defined( MATCAP )
+	#if ! defined( STANDARD ) && ! defined( PHONG ) && ! defined( MATCAP ) && ! defined( TOON )
 		varying vec3 vViewPosition;
 	#endif
 

src/renderers/shaders/ShaderChunk/clipping_planes_pars_vertex.glsl.js

@@ -1,5 +1,5 @@
 export default /* glsl */`
-#if NUM_CLIPPING_PLANES > 0 && ! defined( STANDARD ) && ! defined( PHONG ) && ! defined( MATCAP )
+#if NUM_CLIPPING_PLANES > 0 && ! defined( STANDARD ) && ! defined( PHONG ) && ! defined( MATCAP ) && ! defined( TOON )
 	varying vec3 vViewPosition;
 #endif
 `;

src/renderers/shaders/ShaderChunk/clipping_planes_vertex.glsl.js

@@ -1,5 +1,5 @@
 export default /* glsl */`
-#if NUM_CLIPPING_PLANES > 0 && ! defined( STANDARD ) && ! defined( PHONG ) && ! defined( MATCAP )
+#if NUM_CLIPPING_PLANES > 0 && ! defined( STANDARD ) && ! defined( PHONG ) && ! defined( MATCAP ) && ! defined( TOON )
 	vViewPosition = - mvPosition.xyz;
 #endif
 `;