Fix negative chunk coordinate conversion

src/main/java/com/moulberry/axiom/packet/SetBlockPacketListener.java

@@ -46,13 +46,16 @@ public class SetBlockPacketListener implements AxiomPacketListener {
         int x = getX.invoke(pos);
         int y = getY.invoke(pos);
         int z = getZ.invoke(pos);
+        int cx = x / 16 - (x < 0 ? 1 : 0);
+        int cy = y / 16 - (y < 0 ? 1 : 0);
+        int cz = z / 16 - (z < 0 ? 1 : 0);
 
         // Update blocks
-        if(RegionProtection.getProtection.apply(player, world).canBuildInSection(x / 16, y / 16, z / 16)) {
+        if(RegionProtection.getProtection.apply(player, world).canBuildInSection(cx, cy, cz)) {
             if (updateNeighbors) {
                 setBlock.invoke(AxiomPaper.convert(player.getWorld()), pos, state, 3);
             } else {
-                ChunkSectionModifier section = new ChunkSectionModifier(player.getWorld(), x / 16, y / 16, z / 16);
+                ChunkSectionModifier section = new ChunkSectionModifier(player.getWorld(), cx, cy, cz);
                 section.setState(x & 0xF, y & 0xF, z & 0xF, state);
                 section.finish();
             }