cleanup Buf struct

src/grid.rs

@@ -71,7 +71,7 @@ impl Grid {
             height,
             data,
             config: PopulationConfig::new(rng),
-            buf: Buf::new(width, height, vec![0.0; width * height]),
+            buf: Buf::new(width, height),
             blur: Blur::new(width),
             agents,
         }