When I downloaded MCMMO version 1.5.00 on my spigot 1.7.9 R02 server, It didn't respond with any command due to this error. Please respond to this asap.

21:01:01 ERROR]: Error occurred while disabling mcMMO v1.5.00-b3547 (Is it up to date?)
java.lang.ExceptionInInitializerError
at com.gmail.nossr50.mcMMO.onDisable(mcMMO.java:206) ~[?:?]
at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:318) ~[server.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at org.bukkit.plugin.java.JavaPluginLoader.disablePlugin(JavaPluginLoader.java:356) [server.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at org.bukkit.plugin.SimplePluginManager.disablePlugin(SimplePluginManager.java:431) [server.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at com.gmail.nossr50.mcMMO.onEnable(mcMMO.java:193) [mcMMO.jar:?]
at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:316) [server.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:332) [server.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:412) [server.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at org.bukkit.craftbukkit.v1_7_R4.CraftServer.loadPlugin(CraftServer.java:476) [server.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at org.bukkit.craftbukkit.v1_7_R4.CraftServer.enablePlugins(CraftServer.java:394) [server.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at net.minecraft.server.v1_7_R4.DedicatedServer.init(DedicatedServer.java:153) [server.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at net.minecraft.server.v1_7_R4.MinecraftServer.run(MinecraftServer.java:458) [server.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at net.minecraft.server.v1_7_R4.ThreadServerApplication.run(SourceFile:628) [server.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
Caused by: java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
at java.util.ArrayList.rangeCheck(Unknown Source) ~[?:1.8.0_91]
at java.util.ArrayList.get(Unknown Source) ~[?:1.8.0_91]
at org.bukkit.craftbukkit.v1_7_R4.CraftOfflinePlayer.<init>(CraftOfflinePlayer.java:34) ~[server.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at org.bukkit.craftbukkit.v1_7_R4.CraftServer.getOfflinePlayer(CraftServer.java:1440) ~[server.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at org.bukkit.craftbukkit.v1_7_R4.CraftServer.getOfflinePlayer(CraftServer.java:1412) ~[server.jar:git-Spigot-1.7.9-R0.2-208-ge0f2e95]
at com.gmail.nossr50.util.scoreboards.ScoreboardManager.getOfflinePlayer(ScoreboardManager.java:133) ~[?:?]
at com.gmail.nossr50.util.scoreboards.ScoreboardManager.getOfflinePlayer(ScoreboardManager.java:121) ~[?:?]
at com.gmail.nossr50.util.scoreboards.ScoreboardManager.<clinit>(ScoreboardManager.java:43) ~[?:?]
... 13 more