Clicking Play Brings me back to launcher page repeatedly

Put the summary of the bug you're having here

What I expected to happen was...:
When I clicked "play" on the launcher it should take me to the minecraft title screen.

What actually happened was...:
When I click on "play" it brings me back to the launcher on a part called "game output"

This is the message I see:

[19:02:37] [Client thread/INFO]: Setting user: CHM9999

[19:02:37] [Client thread/INFO]: (Session ID is token:d116694cc9f94e618540926e9551c6af:067dab1e4e774f27a4b9b09df26dc95f)

Exception in thread "Client thread" com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING at line 1 column 1

at com.google.gson.Gson.fromJson(Gson.java:815)

at com.google.gson.Gson.fromJson(Gson.java:768)

at lu.b(SourceFile:151)

at lu.<init>(SourceFile:43)

at net.minecraft.server.MinecraftServer.<init>(SourceFile:155)

at bpp.<init>(SourceFile:41)

at avf.<init>(SourceFile:293)

at net.minecraft.client.main.Main.main(SourceFile:124)

Caused by: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING at line 1 column 1

at com.google.gson.stream.JsonReader.beginArray(JsonReader.java:338)

at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:79)

at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:60)

at com.google.gson.Gson.fromJson(Gson.java:803)

... 7 more

Java HotSpot(TM) 64-Bit Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release