Actually initialize GameModes and WeatherTypes.

worldedit-bukkit/src/main/java/com/sk89q/worldedit/bukkit/WorldEditPlugin.java

@@ -44,8 +44,10 @@ import com.sk89q.worldedit.world.block.BlockState;
 import com.sk89q.worldedit.world.block.BlockType;
 import com.sk89q.worldedit.world.block.FuzzyBlockState;
 import com.sk89q.worldedit.world.entity.EntityType;
+import com.sk89q.worldedit.world.gamemode.GameModes;
 import com.sk89q.worldedit.world.item.ItemCategory;
 import com.sk89q.worldedit.world.item.ItemType;
+import com.sk89q.worldedit.world.weather.WeatherTypes;
 import org.bstats.bukkit.Metrics;
 import org.bukkit.Bukkit;
 import org.bukkit.Material;
@@ -173,6 +175,9 @@ public class WorldEditPlugin extends JavaPlugin implements TabCompleter {
                 EntityType.REGISTRY.register("minecraft:" + lowerCaseMcId, new EntityType("minecraft:" + lowerCaseMcId));
             }
         }
+        // ... :|
+        GameModes.get("");
+        WeatherTypes.get("");
     }
 
     private void setupTags() {

worldedit-core/src/main/java/com/sk89q/worldedit/world/block/BlockTypes.java

@@ -628,7 +628,8 @@ public final class BlockTypes {
     private BlockTypes() {
     }
 
-    public static @Nullable BlockType get(final String id) {
+    @Nullable
+    public static BlockType get(final String id) {
         return BlockType.REGISTRY.get(id);
     }
 }

worldedit-core/src/main/java/com/sk89q/worldedit/world/gamemode/GameModes.java

@@ -21,7 +21,7 @@ package com.sk89q.worldedit.world.gamemode;
 
 import javax.annotation.Nullable;
 
-public class GameModes {
+public final class GameModes {
 
     public static final GameMode SURVIVAL = register("survival");
     public static final GameMode CREATIVE = register("creative");

worldedit-core/src/main/java/com/sk89q/worldedit/world/weather/WeatherTypes.java

@@ -21,23 +21,25 @@ package com.sk89q.worldedit.world.weather;
 
 import javax.annotation.Nullable;
 
-public class WeatherTypes {
+public final class WeatherTypes {
 
-    static {
+    public static final WeatherType CLEAR = register("clear");
-        // This isn't really a proper registry - so inject these before they're obtained.
+    public static final WeatherType RAIN = register("rain");
-        WeatherType.REGISTRY.register("clear", new WeatherType("clear"));
+    public static final WeatherType THUNDER_STORM = register("thunder_storm");
-        WeatherType.REGISTRY.register("rain", new WeatherType("rain"));
-        WeatherType.REGISTRY.register("thunder_storm", new WeatherType("thunder_storm"));
-    }
-
-    @Nullable public static final WeatherType CLEAR = get("clear");
-    @Nullable public static final WeatherType RAIN = get("rain");
-    @Nullable public static final WeatherType THUNDER_STORM = get("thunder_storm");
 
     private WeatherTypes() {
     }
 
-    public static @Nullable WeatherType get(final String id) {
+    private static WeatherType register(String id) {
+        return register(new WeatherType(id));
+    }
+
+    public static WeatherType register(WeatherType weather) {
+        return WeatherType.REGISTRY.register(weather.getId(), weather);
+    }
+
+    @Nullable
+    public static WeatherType get(final String id) {
         return WeatherType.REGISTRY.get(id);
     }
 }