Remove null values in TileEntity tick list

Because who wouldn't want to tick a null tile entity right?
Fixes GH-851

Spigot-API-Patches/0032-Add-MetadataStoreBase.removeAll-Plugin.patch

@@ -1,4 +1,4 @@
-From 1a59075c01dbe0d53bd6fbfd94ccb1ef6a047a6a Mon Sep 17 00:00:00 2001
+From deead5d94a52ef9bf9f10ca6bb8771cdcabb587f Mon Sep 17 00:00:00 2001
 From: Aikar <aikar@aikar.co>
 Date: Tue, 16 Jul 2013 21:26:50 -0400
 Subject: [PATCH] Add MetadataStoreBase.removeAll(Plugin)
@@ -9,10 +9,11 @@ diff --git a/src/main/java/org/bukkit/metadata/MetadataStoreBase.java b/src/main
 index 64c0f0a7..6da6abd8 100644
 --- a/src/main/java/org/bukkit/metadata/MetadataStoreBase.java
 +++ b/src/main/java/org/bukkit/metadata/MetadataStoreBase.java
-@@ -125,6 +125,26 @@ public abstract class MetadataStoreBase<T> {
+@@ -124,6 +124,26 @@ public abstract class MetadataStoreBase<T> {
+         }
      }
  
-     /**
++    /**
 +     * Removes all metadata in the metadata store that originates from the
 +     * given plugin.
 +     *
@@ -32,10 +33,9 @@ index 64c0f0a7..6da6abd8 100644
 +        }
 +    }
 +
-+    /**
+     /**
       * Creates a unique name for the object receiving metadata by combining
       * unique data from the subject with a metadataKey.
-      * <p>
 -- 
-2.12.2
+2.14.1