Permit empty keys in CompoundTag

Vanilla for example emits these in HeterogenousListCollector

Author: aromaa

src/main/java/org/spongepowered/common/data/persistence/NBTTranslator.java

@@ -48,7 +48,6 @@
 import org.spongepowered.api.data.persistence.DataView;
 import org.spongepowered.api.data.persistence.InvalidDataException;
 import org.spongepowered.common.util.Constants;
-import org.spongepowered.common.util.Preconditions;
 
 import java.util.List;
 import java.util.Map;
@@ -180,7 +179,6 @@ private static void setInternal(Tag base, byte type, DataView view, String key)
         Objects.requireNonNull(base, "base");
         Objects.requireNonNull(view, "view");
         Objects.requireNonNull(key, "key");
-        Preconditions.checkArgument(!key.isEmpty(), "key is empty");
         switch (type) {
             case Constants.NBT.TAG_BYTE:
                 if (key.contains(NBTTranslator.BOOLEAN_IDENTIFIER)) {