SPIGOT-5482: Structure Block setUsageMode encounters NullpointerException

nms-patches/TileEntityStructure.patch

@@ -0,0 +1,11 @@
+--- a/net/minecraft/server/TileEntityStructure.java
++++ b/net/minecraft/server/TileEntityStructure.java
+@@ -18,7 +18,7 @@
+     public BlockPosition size;
+     public EnumBlockMirror mirror;
+     public EnumBlockRotation rotation;
+-    private BlockPropertyStructureMode usageMode;
++    public BlockPropertyStructureMode usageMode;
+     public boolean ignoreEntities;
+     private boolean powered;
+     public boolean showAir;

src/main/java/org/bukkit/craftbukkit/block/CraftStructureBlock.java

@@ -105,7 +105,7 @@ public class CraftStructureBlock extends CraftBlockEntityState<TileEntityStructu
 
     @Override
     public void setUsageMode(UsageMode mode) {
-        getSnapshot().setUsageMode(BlockPropertyStructureMode.valueOf(mode.name()));
+        getSnapshot().usageMode = BlockPropertyStructureMode.valueOf(mode.name());
     }
 
     @Override
@@ -177,6 +177,14 @@ public class CraftStructureBlock extends CraftBlockEntityState<TileEntityStructu
         return getSnapshot().metadata;
     }
 
+    @Override
+    protected void applyTo(TileEntityStructure tileEntity) {
+        super.applyTo(tileEntity);
+
+        // Ensure block type is correct
+        tileEntity.setUsageMode(tileEntity.getUsageMode());
+    }
+
     private static boolean isBetween(int num, int min, int max) {
         return num >= min && num <= max;
     }