Here is the error that I got after trying to launch the game:

[17:34:27 FATAL]: Fatal error launching game. Report this to http://bugs.mojang.com please!
java.io.FileNotFoundException: File 'C:\Users\Dan\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) [?:1.7.0_71]
at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.7.0_71]
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [?:1.7.0_71]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [?:1.7.0_71]
at java.lang.Thread.run(Unknown Source) [?:1.7.0_71]
[17:34:40 ERROR]: Game ended with bad state (exit code -1073741819)
[17:34:40 INFO]: Ignoring visibility rule and showing launcher due to a game crash
[17:34:40 INFO]: Deleting C:\Users\Dan\AppData\Roaming\.minecraft\versions\1.8\1.8-natives-15640754670792
[17:34:40 WARN]: Couldn't delete C:\Users\Dan\AppData\Roaming\.minecraft\versions\1.8\1.8-natives-15640754670792 - scheduling for deletion upon exit