Fix palette size when filling to 0

src/main/java/net/minestom/server/instance/palette/PaletteImpl.java

@@ -147,7 +147,7 @@ final class PaletteImpl implements Palette, Cloneable {
             block |= (long) value << i * bitsPerEntry;
         }
         Arrays.fill(values, block);
-        this.count = maxSize();
+        this.count = placedAir ? 0 : maxSize();
     }
 
     @Override

src/test/java/net/minestom/server/instance/PaletteTest.java

@@ -96,6 +96,16 @@ public class PaletteTest {
                     }
                 }
             }
+
+            palette.fill(0);
+            assertEquals(0, palette.size());
+            for (int y = 0; y < palette.dimension(); y++) {
+                for (int x = 0; x < palette.dimension(); x++) {
+                    for (int z = 0; z < palette.dimension(); z++) {
+                        assertEquals(0, palette.get(x, y, z));
+                    }
+                }
+            }
         }
     }