bsp_loader: fix utf8 brush model

lib/bsp_loader/src/bsp.rs

@@ -53,9 +53,9 @@ fn add_brush<'a>(
 		rendercolor.b as f32
 	])/255.0).extend(1.0);
 
-	match model.split_at(1){
+	match model.chars().next(){
 		// The first character of brush.model is '*'
-		("*",id_str)=>match id_str.parse(){
+		Some('*')=>match model[1..].parse(){
 			Ok(mesh_id)=>{
 				let mesh=model::MeshId::new(mesh_id);
 				world_models.push(