retrieve BlockEntities tag in v3 schematics optionally

Author: PierreSchwang

worldedit-core/src/main/java/com/sk89q/worldedit/extent/clipboard/io/sponge/SpongeSchematicV3Reader.java

@@ -143,7 +143,7 @@ private void decodeBlocksIntoClipboard(VersionedDataFixer fixer, LinCompoundTag
         );
 
         byte[] blocks = blockContainer.getTag("Data", LinTagType.byteArrayTag()).value();
-        LinListTag<LinCompoundTag> blockEntities = blockContainer.getListTag("BlockEntities", LinTagType.compoundTag());
+        LinListTag<LinCompoundTag> blockEntities = blockContainer.findListTag("BlockEntities", LinTagType.compoundTag());
 
         ReaderUtil.initializeClipboardFromBlocks(
             clipboard, palette, blocks, blockEntities, fixer, true