Fixed NullPointerException when performing a preview with invalid data (fixes #862)

src/main/java/net/coreprotect/utility/BlockUtils.java

@@ -165,6 +165,9 @@ public class BlockUtils {
         if (blockData == null) {
             blockData = createBlockData(type);
         }
+        if (blockData == null) {
+            return;
+        }
 
         if (!update) {
             setTypeAndData(block, type, blockData, update);

src/main/java/net/coreprotect/utility/Util.java

@@ -21,6 +21,10 @@ public class Util extends Queue {
     }
 
     public static void sendBlockChange(Player player, Location location, BlockData blockData) {
+        if (blockData == null) {
+            return;
+        }
+
         player.sendBlockChange(location, blockData);
     }
 }