Correctly nullcheck biome types in //setbiome

Biome changing is no longer supported in SpoutAPI, will reimplement when I have time

src/main/java/com/sk89q/worldedit/commands/BiomeCommands.java

@@ -129,6 +129,11 @@ public class BiomeCommands {
                           EditSession editSession) throws WorldEditException {
 
         final BiomeType target = we.getServer().getBiomes().get(args.getString(0));
+        if (target == null) {
+            player.printError("Biome '" + args.getString(0) + "' does not exist!");
+            return;
+        }
+
         if (args.hasFlag('p')) {
             Vector2D pos = player.getPosition().toVector2D();
             player.getWorld().setBiome(pos, target);

src/main/java/com/sk89q/worldedit/spout/SpoutWorld.java

@@ -213,7 +213,8 @@ public class SpoutWorld extends LocalWorld {
         if (biome instanceof SpoutBiomeType &&
                 world.getGenerator() instanceof BiomeGenerator) {
             BiomeGenerator gen = (BiomeGenerator) world.getGenerator();
-            gen.setBiome(new Vector3(pt.getBlockX(), 0, pt.getBlockZ()), ((SpoutBiomeType) biome).getSpoutBiome());
+            throw new UnsupportedOperationException("Biome changing is not yet supported in Spout");
+            //gen.setBiome(new Vector3(pt.getBlockX(), 0, pt.getBlockZ()), ((SpoutBiomeType) biome).getSpoutBiome());
         }
     }