Internal server error

I keep getting "Internal server error" when I try to join my server but my friend can join it
Here's the log part:
2018-07-20 00:44:53 [WARNING] Failed to handle packet for Death_Prevails [/**.**.**.**:63066]: java.lang.NullPointerException

19java.lang.NullPointerException

20 at net.minecraft.server.management.ServerConfigurationManager.func_72355_a(ServerConfigurationManager.java:125)

21 at net.minecraft.network.NetLoginHandler.completeConnection(NetLoginHandler.java:201)

22 at cpw.mods.fml.common.network.FMLNetworkHandler.handleClientConnection(FMLNetworkHandler.java:167)

23 at cpw.mods.fml.common.network.FMLNetworkHandler.onConnectionReceivedFromClient(FMLNetworkHandler.java:121)

24 at net.minecraft.network.NetLoginHandler.func_72529_d(NetLoginHandler.java:185)

25 at net.minecraft.network.NetLoginHandler.func_72532_c(NetLoginHandler.java:71)

26 at net.minecraft.server.ServerListenThread.func_71766_a(ServerListenThread.java:55)

27 at net.minecraft.server.dedicated.DedicatedServerListenThread.func_71747_b(SourceFile:29)

28 at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:691)

29 at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:276)

30 at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:587)

31 at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:484)

32 at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)

332018-07-20 00:44:54 [SEVERE] Reached end of stream for /**.**.**.**

342018-07-20 00:44:56 [SEVERE] Reached end of stream for /**.**.**.**

352018-07-20 00:45:32 [INFO] Death_Prevails[/**.**.**.**:63120] logged in with entity id 388 at (-1596.5, 116.0, 2484.5)

362018-07-20 00:45:32 [INFO] Disconnecting Death_Prevails [/**.**.**.**:63120]: Internal server error

372018-07-20 00:45:32 [WARNING] Failed to handle packet for Death_Prevails [/**.**.**.**:63120]: java.lang.NullPointerException

38java.lang.NullPointerException

39 at net.minecraft.server.management.ServerConfigurationManager.func_72355_a(ServerConfigurationManager.java:125)

40 at net.minecraft.network.NetLoginHandler.completeConnection(NetLoginHandler.java:201)

41 at cpw.mods.fml.common.network.FMLNetworkHandler.handleClientConnection(FMLNetworkHandler.java:167)

42 at cpw.mods.fml.common.network.FMLNetworkHandler.onConnectionReceivedFromClient(FMLNetworkHandler.java:121)

43 at net.minecraft.network.NetLoginHandler.func_72529_d(NetLoginHandler.java:185)

44 at net.minecraft.network.NetLoginHandler.func_72532_c(NetLoginHandler.java:71)

45 at net.minecraft.server.ServerListenThread.func_71766_a(ServerListenThread.java:55)

46 at net.minecraft.server.dedicated.DedicatedServerListenThread.func_71747_b(SourceFile:29)

47 at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:691)

48 at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:276)

49 at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:587)

50 at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:484)

51 at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)

522018-07-20 00:45:33 [SEVERE] Reached end of stream for /**.**.**.**

532018-07-20 00:45:34 [SEVERE] Reached end of stream for /**.**.**.**

542018-07-20 00:47:40 [SEVERE] Reached end of stream for /**.**.**.**

552018-07-20 00:47:40 [INFO] Death_Prevails [/**.**.**.**:63457] lost connection

562018-07-20 00:48:16 [SEVERE] Reached end of stream for /**.**.**.**

The world file got corrupted later anyways on my friends side so we just deleted the world.

Thank you for the info, I'll do that next time it happens