MobArena Error

Error occurred while enabling MobArena v0.94.3.24 (Is it up to date?): null; mapping values are not allowed here
mapping values are not allowed here
 in "<reader>", line 7, column 16:
            classes:
                   ^

	at org.yaml.snakeyaml.scanner.ScannerImpl.fetchValue(ScannerImpl.java:733)
	at org.yaml.snakeyaml.scanner.ScannerImpl.fetchMoreTokens(ScannerImpl.java:305)
	at org.yaml.snakeyaml.scanner.ScannerImpl.checkToken(ScannerImpl.java:179)
	at org.yaml.snakeyaml.parser.ParserImpl$ParseBlockMappingKey.produce(ParserImpl.java:563)
	at org.yaml.snakeyaml.parser.ParserImpl.peekEvent(ParserImpl.java:161)
	at org.yaml.snakeyaml.parser.ParserImpl.checkEvent(ParserImpl.java:146)
	at org.yaml.snakeyaml.composer.Composer.composeMappingNode(Composer.java:230)
	at org.yaml.snakeyaml.composer.Composer.composeNode(Composer.java:160)
	at org.yaml.snakeyaml.composer.Composer.composeDocument(Composer.java:123)
	at org.yaml.snakeyaml.composer.Composer.getSingleNode(Composer.java:106)
	at org.yaml.snakeyaml.constructor.BaseConstructor.getSingleData(BaseConstructor.java:121)
	at org.yaml.snakeyaml.Yaml.loadFromReader(Yaml.java:480)
	at org.yaml.snakeyaml.Yaml.load(Yaml.java:423)
	at org.bukkit.util.config.Configuration.load(Configuration.java:89)
	at com.garbagemule.MobArena.MobArena.loadConfig(Unknown Source)
	at com.garbagemule.MobArena.MobArena.onEnable(Unknown Source)
	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:188)
	at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:968)
	at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:280)
	at org.bukkit.craftbukkit.CraftServer.loadPlugin(CraftServer.java:186)
	at org.bukkit.craftbukkit.CraftServer.enablePlugins(CraftServer.java:169)
	at org.bukkit.craftbukkit.CraftServer.reload(CraftServer.java:436)
	at org.bukkit.Bukkit.reload(Bukkit.java:187)
	at org.bukkit.command.defaults.ReloadCommand.execute(ReloadCommand.java:22)
	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:165)
	at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:378)
	at net.minecraft.server.NetServerHandler.handleCommand(NetServerHandler.java:757)
	at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:722)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:715)
	at net.minecraft.server.Packet3Chat.a(Packet3Chat.java:33)
	at net.minecraft.server.NetworkManager.b(NetworkManager.java:226)
	at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:93)
	at net.minecraft.server.NetworkListenThread.a(SourceFile:108)
	at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:527)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:425)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:457)