Fix some blockstate consistency issues.

src/main/java/org/bukkit/craftbukkit/block/CraftBanner.java

@@ -97,7 +97,7 @@ public class CraftBanner extends CraftBlockState implements Banner {
 
     @Override
     public boolean update(boolean force, boolean applyPhysics) {
-        boolean result = (isPlaced()) ? super.update(force, applyPhysics) : true;
+        boolean result = super.update(force, applyPhysics);
 
         if (result) {
             banner.color = EnumColor.fromInvColorIndex(base.getDyeData());

src/main/java/org/bukkit/craftbukkit/block/CraftBlockState.java

@@ -151,7 +151,9 @@ public class CraftBlockState implements BlockState {
     }
 
     public boolean update(boolean force, boolean applyPhysics) {
-        requirePlaced();
+        if (!isPlaced()) {
+            return true;
+        }
         Block block = getBlock();
 
         if (block.getType() != getType()) {

src/main/java/org/bukkit/craftbukkit/block/CraftCommandBlock.java

@@ -44,7 +44,7 @@ public class CraftCommandBlock extends CraftBlockState implements CommandBlock {
     }
 
     public boolean update(boolean force, boolean applyPhysics) {
-        boolean result = (isPlaced()) ? super.update(force, applyPhysics) : true;
+        boolean result = super.update(force, applyPhysics);
 
         if (result) {
             commandBlock.getCommandBlock().setCommand(command);

src/main/java/org/bukkit/craftbukkit/block/CraftComparator.java

@@ -4,10 +4,9 @@ import net.minecraft.server.TileEntity;
 import net.minecraft.server.TileEntityComparator;
 import org.bukkit.Material;
 import org.bukkit.block.Block;
-import org.bukkit.block.EnderChest;
 import org.bukkit.craftbukkit.CraftWorld;
 
-public class CraftComparator extends CraftBlockState implements EnderChest {
+public class CraftComparator extends CraftBlockState {
 
     private final CraftWorld world;
     private final TileEntityComparator comparator;

src/main/java/org/bukkit/craftbukkit/block/CraftDaylightDetector.java

@@ -4,10 +4,9 @@ import net.minecraft.server.TileEntity;
 import net.minecraft.server.TileEntityLightDetector;
 import org.bukkit.Material;
 import org.bukkit.block.Block;
-import org.bukkit.block.EnderChest;
 import org.bukkit.craftbukkit.CraftWorld;
 
-public class CraftDaylightDetector extends CraftBlockState implements EnderChest {
+public class CraftDaylightDetector extends CraftBlockState {
 
     private final CraftWorld world;
     private final TileEntityLightDetector detector;

src/main/java/org/bukkit/craftbukkit/block/CraftFlowerPot.java

@@ -8,23 +8,25 @@ import org.bukkit.block.Block;
 import org.bukkit.block.FlowerPot;
 import org.bukkit.craftbukkit.CraftWorld;
 import org.bukkit.craftbukkit.inventory.CraftItemStack;
-import org.bukkit.craftbukkit.util.CraftMagicNumbers;
 import org.bukkit.material.MaterialData;
 
 public class CraftFlowerPot extends CraftBlockState implements FlowerPot {
 
     private final TileEntityFlowerPot pot;
+    private MaterialData contents;
 
     public CraftFlowerPot(Block block) {
         super(block);
 
         pot = (TileEntityFlowerPot) ((CraftWorld) block.getWorld()).getTileEntityAt(getX(), getY(), getZ());
+        contents = (pot.getItem() == null) ? null : CraftItemStack.asBukkitCopy(pot.getContents()).getData();
     }
 
-    public CraftFlowerPot(Material material, TileEntityFlowerPot pot) {
+    public CraftFlowerPot(Material material, TileEntityFlowerPot te) {
         super(material);
 
-        this.pot = pot;
+        pot = te;
+        contents = (pot.getItem() == null) ? null : CraftItemStack.asBukkitCopy(pot.getContents()).getData();
     }
 
     @Override
@@ -34,15 +36,23 @@ public class CraftFlowerPot extends CraftBlockState implements FlowerPot {
 
     @Override
     public MaterialData getContents() {
-        return (pot.d() == null) ? null : CraftMagicNumbers.getMaterial(pot.getItem()).getNewData((byte) pot.getData()); // PAIL: rename
+        return contents;
     }
 
     @Override
     public void setContents(MaterialData item) {
-        if (item == null) {
-            pot.setContents(ItemStack.a);
-        } else {
-            pot.setContents(CraftItemStack.asNMSCopy(item.toItemStack()));
+        contents = item;
+    }
+
+    @Override
+    public boolean update(boolean force, boolean applyPhysics) {
+        boolean result = super.update(force, applyPhysics);
+
+        if (result) {
+            pot.setContents(contents == null ? ItemStack.a : CraftItemStack.asNMSCopy(contents.toItemStack(1)));
+            pot.update();
         }
+
+        return result;
     }
 }