Prevent NPE in CraftSign

This commit prevents the constructor of CraftSign throwing an NPE when it cannot get the sign tile entity. Instead it will fallback to a 4 empty lined sign, and not try to do anything to those lines on .update().

@TheDgtl

CraftBukkit-Patches/0041-Prevent-NPE-in-CraftSign.patch

@@ -0,0 +1,39 @@
+From 289f93ad3e999628f5d13a5da0fa2939cccbb5dd Mon Sep 17 00:00:00 2001
+From: md_5 <md_5@live.com.au>
+Date: Mon, 18 Mar 2013 20:01:44 +1100
+Subject: [PATCH] Prevent NPE in CraftSign
+
+This commit prevents the constructor of CraftSign throwing an NPE when it cannot get the sign tile entity. Instead it will fallback to a 4 empty lined sign, and not try to do anything to those lines on .update().
+---
+ src/main/java/org/bukkit/craftbukkit/block/CraftSign.java | 8 +++++++-
+ 1 file changed, 7 insertions(+), 1 deletion(-)
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/block/CraftSign.java b/src/main/java/org/bukkit/craftbukkit/block/CraftSign.java
+index 8e8a1c5..8b7d226 100644
+--- a/src/main/java/org/bukkit/craftbukkit/block/CraftSign.java
++++ b/src/main/java/org/bukkit/craftbukkit/block/CraftSign.java
+@@ -14,6 +14,12 @@ public class CraftSign extends CraftBlockState implements Sign {
+ 
+         CraftWorld world = (CraftWorld) block.getWorld();
+         sign = (TileEntitySign) world.getTileEntityAt(getX(), getY(), getZ());
++        // Spigot start
++        if (sign == null) {
++            lines = new String[4];
++            return;
++        }
++        // Spigot end
+         lines = new String[sign.lines.length];
+         System.arraycopy(sign.lines, 0, lines, 0, lines.length);
+     }
+@@ -34,7 +40,7 @@ public class CraftSign extends CraftBlockState implements Sign {
+     public boolean update(boolean force) {
+         boolean result = super.update(force);
+ 
+-        if (result) {
++        if (result && sign != null) { // Spigot, add null check
+             for(int i = 0; i < 4; i++) {
+                 if(lines[i] != null) {
+                     sign.lines[i] = lines[i];
+-- 
+1.8.1-rc2
+