Error spam on old Bukkit versions while there's nothing wrong

[jobukkit]

java.lang.NoSuchMethodError:         org.bukkit.Bukkit.getOfflinePlayer(Ljava/util/UUID;)Lorg/bukkit/OfflinePlayer;
[20:44:39] [Server thread/WARN]: at net.jopv.minecraft.bukkit.minecraftpush.MinecraftPush.push(MinecraftPush.java:316)
[20:44:39] [Server thread/WARN]: at net.jopv.minecraft.bukkit.minecraftpush.MinecraftPush.push(MinecraftPush.java:285)
[20:44:39] [Server thread/WARN]: at net.jopv.minecraft.bukkit.minecraftpush.MinecraftPush.onPlayerJoin(MinecraftPush.java:262)
[20:44:39] [Server thread/WARN]: at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[20:44:39] [Server thread/WARN]: at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
[20:44:39] [Server thread/WARN]: at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
[20:44:39] [Server thread/WARN]: at java.lang.reflect.Method.invoke(Unknown Source)
[20:44:39] [Server thread/WARN]: at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:318)
[20:44:39] [Server thread/WARN]: at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
[20:44:39] [Server thread/WARN]: at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:486)
[20:44:39] [Server thread/WARN]: at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:471)
[20:44:39] [Server thread/WARN]: at net.minecraft.server.v1_7_R1.PlayerList.c(PlayerList.java:225)
[20:44:39] [Server thread/WARN]: at net.minecraft.server.v1_7_R1.PlayerList.a(PlayerList.java:116)
[20:44:39] [Server thread/WARN]: at net.minecraft.server.v1_7_R1.LoginListener.c(LoginListener.java:78)
[20:44:39] [Server thread/WARN]: at net.minecraft.server.v1_7_R1.LoginListener.a(LoginListener.java:42)
[20:44:39] [Server thread/WARN]: at net.minecraft.server.v1_7_R1.NetworkManager.a(NetworkManager.java:149)
[20:44:39] [Server thread/WARN]: at net.minecraft.server.v1_7_R1.ServerConnection.c(SourceFile:134)
[20:44:39] [Server thread/WARN]: at net.minecraft.server.v1_7_R1.MinecraftServer.u(MinecraftServer.java:655)
[20:44:39] [Server thread/WARN]: at net.minecraft.server.v1_7_R1.DedicatedServer.u(DedicatedServer.java:250)
[20:44:39] [Server thread/WARN]: at net.minecraft.server.v1_7_R1.MinecraftServer.t(MinecraftServer.java:545)
[20:44:39] [Server thread/WARN]: at net.minecraft.server.v1_7_R1.MinecraftServer.run(MinecraftServer.java:457)
[20:44:39] [Server thread/WARN]: at net.minecraft.server.v1_7_R1.ThreadServerApplication.run(SourceFile:617)