Unable to start installed Minecraft modpack

Hey, any idea what might be wrong?

Quote

[12:51:39] [Client thread/ERROR]: Unable to launch
java.lang.reflect.InvocationTargetException: null
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_51]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_51]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_51]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[?:1.8.0_51]
    at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [launchwrapper-1.12.jar:?]
    at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?]
Caused by: java.lang.NoClassDefFoundError: net/minecraft/world/NextTickListEntry$c
    at net.optifine.reflect.Reflector.<clinit>(Reflector.java:211) ~[Reflector.class:?]
    at net.minecraft.crash.CrashReport.func_71504_g(CrashReport.java:138) ~[b.class:?]
    at net.minecraft.crash.CrashReport.<init>(CrashReport.java:54) ~[b.class:?]
    at net.minecraft.crash.CrashReport.func_85055_a(CrashReport.java:425) ~[b.class:?]
    at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:382) ~[bib.class:?]
    at net.minecraft.client.main.Main.main(SourceFile:123) ~[Main.class:?]
    ... 6 more
Caused by: java.lang.ClassNotFoundException: net.minecraft.world.NextTickListEntry$c
    at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191) ~[launchwrapper-1.12.jar:?]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_51]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_51]
    at net.optifine.reflect.Reflector.<clinit>(Reflector.java:211) ~[Reflector.class:?]
    at net.minecraft.crash.CrashReport.func_71504_g(CrashReport.java:138) ~[b.class:?]
    at net.minecraft.crash.CrashReport.<init>(CrashReport.java:54) ~[b.class:?]
    at net.minecraft.crash.CrashReport.func_85055_a(CrashReport.java:425) ~[b.class:?]
    at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:382) ~[bib.class:?]
    at net.minecraft.client.main.Main.main(SourceFile:123) ~[Main.class:?]
    ... 6 more
Caused by: java.lang.NullPointerException
[12:51:39] [Client thread/INFO]: [java.lang.ThreadGroup:uncaughtException:1052]: net.minecraftforge.fml.relauncher.FMLSecurityManager$ExitTrappedException
[12:51:39] [Client thread/INFO]: [java.lang.ThreadGroup:uncaughtException:1052]:     at net.minecraftforge.fml.relauncher.FMLSecurityManager.checkPermission(FMLSecurityManager.java:49)
[12:51:39] [Client thread/INFO]: [java.lang.ThreadGroup:uncaughtException:1052]:     at java.lang.SecurityManager.checkExit(SecurityManager.java:761)
[12:51:39] [Client thread/INFO]: [java.lang.ThreadGroup:uncaughtException:1052]:     at java.lang.Runtime.exit(Runtime.java:107)
[12:51:39] [Client thread/INFO]: [java.lang.ThreadGroup:uncaughtException:1052]:     at java.lang.System.exit(System.java:971)
[12:51:39] [Client thread/INFO]: [java.lang.ThreadGroup:uncaughtException:1052]:     at net.minecraft.launchwrapper.Launch.launch(Launch.java:138)
[12:51:39] [Client thread/INFO]: [java.lang.ThreadGroup:uncaughtException:1052]:     at net.minecraft.launchwrapper.Launch.main(Launch.java:28)