Fix potential NullPointerExceptions

src/main/java/com/Acrobot/ChestShop/Listeners/GarbageTextListener.java

@@ -16,6 +16,7 @@ public class GarbageTextListener implements Listener {
     public static void filterGarbage(SignChangeEvent event) {
         for (int i = 0; i < 4; ++i) {
             String line = event.getLine(i);
+            if (line != null) {
                 StringBuilder output = new StringBuilder(line.length());
 
                 for (char character : line.toCharArray()) {
@@ -28,3 +29,4 @@ public class GarbageTextListener implements Listener {
             }
         }
     }
+}

src/main/java/com/Acrobot/ChestShop/Listeners/PostTransaction/EmptyShopDeleter.java

@@ -52,7 +52,9 @@ public class EmptyShopDeleter implements Listener {
         sign.getBlock().setType(Material.AIR);
 
         if (Properties.REMOVE_EMPTY_CHESTS && !ChestShopSign.isAdminShop(ownerInventory) && InventoryUtil.isEmpty(ownerInventory)) {
+            if (connectedContainer != null) {
                 connectedContainer.getBlock().setType(Material.AIR);
+            }
         } else {
             if (!signType.isItem()) {
                 try {

src/main/java/com/Acrobot/ChestShop/Utils/uBlock.java

@@ -221,7 +221,7 @@ public class uBlock {
             Sign sign = (Sign) faceBlock.getState();
 
             Container signContainer = findConnectedContainer(sign);
-            if (!chestBlock.equals(signContainer.getBlock())) {
+            if (signContainer == null || !chestBlock.equals(signContainer.getBlock())) {
                 continue;
             }