Went into Nether in my single player world, no mods. Had to close for a time, logging out while still in the Nether. Now every time the world is loaded it crashes before being playable.

"[15:57:28 INFO]: Looking for orphaned versions to clean up...
[15:57:28 FATAL]: Fatal error launching game. Report this to http://bugs.mojang.com please!
java.io.FileNotFoundException: File '/Users/davidscannapieco/Library/Application Support/minecraft/assets/indexes/legacy.json' does not exist
at org.apache.commons.io.FileUtils.openInputStream(FileUtils.java:299) ~[launcher.jar:?]
at org.apache.commons.io.FileUtils.readFileToString(FileUtils.java:1711) ~[launcher.jar:?]
at net.minecraft.launcher.Launcher.cleanupOrphanedAssets(Launcher.java:186) ~[launcher.jar:?]
at net.minecraft.launcher.Launcher.performCleanups(Launcher.java:421) ~[launcher.jar:?]
at net.minecraft.launcher.game.MinecraftGameRunner.launchGame(MinecraftGameRunner.java:217) ~[launcher.jar:?]
at com.mojang.launcher.game.runner.AbstractGameRunner.onDownloadJobFinished(AbstractGameRunner.java:177) [launcher.jar:?]
at com.mojang.launcher.updater.download.DownloadJob.popAndDownload(DownloadJob.java:122) [launcher.jar:?]
at com.mojang.launcher.updater.download.DownloadJob.access$000(DownloadJob.java:12) [launcher.jar:?]
at com.mojang.launcher.updater.download.DownloadJob$1.run(DownloadJob.java:86) [launcher.jar:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441) [?:1.6.0_33]
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) [?:1.6.0_33]
at java.util.concurrent.FutureTask.run(FutureTask.java:138) [?:1.6.0_33]
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) [?:1.6.0_33]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) [?:1.6.0_33]
at java.lang.Thread.run(Thread.java:680) [?:1.6.0_33]
[15:57:29 INFO]: Client> [15:57:29] [main/INFO]: Setting user: skanapeko"