This is what I get when click play on minecraft.
The error:
[spoiler]
Completely ignored arguments: [--nativeLauncherVersion, 286]
[21:14:07] [Client thread/INFO]: Setting user: thorval3232
[21:14:07] [Client thread/INFO]: (Session ID is token:5a226a42a0ef4a3e9e75f4ea6082cf45:88ea1958e5694ba7a72218111b7f111b)
Exception in thread "Client thread" java.lang.NullPointerException
at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:213)
at com.google.common.collect.Lists$ReverseList.<init>(Lists.java:767)
at com.google.common.collect.Lists.reverse(Lists.java:759)
at lt.b(SourceFile:156)
at lt.<init>(SourceFile:43)
at net.minecraft.server.MinecraftServer.<init>(SourceFile:155)
at bpo.<init>(SourceFile:41)
at ave.<init>(SourceFile:293)
at net.minecraft.client.main.Main.main(SourceFile:124)
Java HotSpot(TM) 64-Bit Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release
[/spoiler] (Game output, it says)

If you need more information, just ask. Also, I'll send the Launcher Log in an attachment, it's a bit too big for in here.