Minecraft launcher stuck on prepairing

[20:28:55 INFO]: Launcher 3.8.0 started on windows...[20:28:55 INFO]: Launcher 3.8.0 started on windows...[20:28:55 INFO]: Current time is Sep 22, 2019 8:28:55 PM[20:28:55 INFO]: System.getProperty('os.name') == 'Windows 7'[20:28:55 INFO]: System.getProperty('os.version') == '6.1'[20:28:55 INFO]: System.getProperty('os.arch') == 'x86'[20:28:55 INFO]: System.getProperty('java.version') == '1.8.0_221'[20:28:55 INFO]: System.getProperty('java.vendor') == 'Oracle Corporation'[20:28:55 INFO]: System.getProperty('sun.arch.data.model') == '32'[20:28:55 INFO]: JFX is already initialized[20:28:55 INFO]: Refreshing local version list...[20:28:55 INFO]: Refreshing remote version list...[20:28:56 WARNING]: No internet connection![20:28:56 INFO]: Refresh complete.[20:28:57 INFO]: Loaded 1 profile(s); selected '(Default)'[20:29:05 INFO]: Getting syncinfo for selected version[20:29:05 INFO]: Queueing library & version downloads[20:29:06 SEVERE]: Unhandled exception in thread Thread[pool-1-thread-2,5,main]com.google.gson.JsonSyntaxException: duplicate key: null
at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:191)
at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:146)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:93)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:172)
at com.google.gson.Gson.fromJson(Gson.java:795)
at com.google.gson.Gson.fromJson(Gson.java:761)
at com.google.gson.Gson.fromJson(Gson.java:710)
at com.google.gson.Gson.fromJson(Gson.java:682)
at net.minecraft.launcher.updater.RemoteVersionList.getCompleteVersion(Unknown Source)
at net.minecraft.launcher.updater.a.b(Unknown Source)
at net.minecraft.launcher.updater.a.getLatestCompleteVersion(Unknown Source)
at com.mojang.launcher.game.runner.AbstractGameRunner.playGame(Unknown Source)
at net.minecraft.launcher.game.GameLaunchDispatcher$1.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)