The game crach during "loading world"

Put the summary of the bug you're having here

What I expected to happen was...:
spawn in my world

What actually happened was...:
a crash :
java.io.FileNotFoundException: File 'C:\Users\coudert\AppData\Roaming\.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:252) ~[launcher.jar:?]
at net.minecraft.launcher.Launcher.performCleanups(Launcher.java:494) ~[launcher.jar:?]
at net.minecraft.launcher.game.MinecraftGameRunner.launchGame(MinecraftGameRunner.java:221) ~[launcher.jar:?]
at com.mojang.launcher.game.runner.AbstractGameRunner.onDownloadJobFinished(AbstractGameRunner.java:185) [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(Unknown Source) [?:1.8.0_11]
at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_11]
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [?:1.8.0_11]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [?:1.8.0_11]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_11]
[18:29:55 ERROR]: Game ended with bad state (exit code -805306369)
[18:29:55 INFO]: Ignoring visibility rule and showing launcher due to a game crash
[18:29:55 INFO]: Deleting C:\Users\coudert\AppData\Roaming\.minecraft\versions\14w32d\14w32d-natives-171866360795868
[18:29:56 WARN]: Couldn't delete C:\Users\coudert\AppData\Roaming\.minecraft\versions\14w32d\14w32d-natives-171866360795868 - scheduling for deletion upon exit

Steps to Reproduce:
I launch the game ans I load my world