Error When Loading Game.

So, I Was Playing On The Pre-2017 Launcher And I Was Going To Play 18w08b. However, I Accidentially Ran 1.12.2 Instead, And While It Was Starting Up The Game, (Green Bar At Bottom), I Closed The Launcher So That It Wouldn't Load Minecraft. Simple! Then, I Reloaded The Launcher, And Changed My Settings/Version To 18w08b. Then, I Hit Play. It Started Up The Game For A Split Second, The Game Crashed, And Then The Pre-2017 Launcher Showed A VERY Long Crash Report. I Hit Send To Mojang, And Installed The New One. Tried Playing Minecraft On The New Launcher, But It Didn't Work. The Error Message: The game crashed whilst initializing game
The game crashed whilst initializing game
Error: java.lang.IllegalStateException: Not a JSON Object: null (end of error <--)

So, I Was Confused. I Then Tried Deleting The Old Launcher, Trying Minecraft On The New Launcher, But That Error Message Was STILL THERE. Even After Restartig My Computer, It Still Isn't Working.
If I Could Get A Fix, I'd Appreciate It.

Again, Here's The Error Message:

The game crashed whilst initializing game
The game crashed whilst initializing game
Error: java.lang.IllegalStateException: Not a JSON Object: null

(Dunno ANYTHING About JSON.) (Also Note That I'm Using Ver. 2.0.1003 And This Website Doesn't Have That version Listed In "Versions" when selecting a version.)
-TypicalSquib_

FULL CRASH REPORT:

Minecraft Crash Report ----
// But it works on my machine.

Time: 23/02/18 4:14 PM
Description: Initializing game

java.lang.IllegalStateException: Not a JSON Object: null
at com.google.gson.JsonElement.getAsJsonObject(JsonElement.java:90)
at tb.a(SourceFile:72)
at tb.a(SourceFile:65)
at tt.a(SourceFile:35)
at to.a(SourceFile:38)
at tq.a(SourceFile:32)
at byd.a(SourceFile:1170)
at bya.an(SourceFile:437)
at bya.a(SourceFile:366)
at net.minecraft.client.main.Main.main(SourceFile:141)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

– Head –
Thread: Client thread
Stacktrace:
at com.google.gson.JsonElement.getAsJsonObject(JsonElement.java:90)
at tb.a(SourceFile:72)
at tb.a(SourceFile:65)
at tt.a(SourceFile:35)
at to.a(SourceFile:38)
at tq.a(SourceFile:32)
at byd.a(SourceFile:1170)
at bya.an(SourceFile:437)

– Initialization –
Details:
Stacktrace:
at bya.a(SourceFile:366)
at net.minecraft.client.main.Main.main(SourceFile:141)

– System Details –
Details:
Minecraft Version: 18w08b
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 46872256 bytes (44 MB) / 134217728 bytes (128 MB) up to 1073741824 bytes (1024 MB)
JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=16M
Launched Version: 18w08b
LWJGL: 3.1.2 build 29
OpenGL: Intel(R) HD Graphics GL version 4.0.0 - Build 10.18.10.4358, Intel
GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

Using VBOs: Yes
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: novaskin (incompatible)
Current Language: ~_ERROR~ NullPointerException: null
Profiler Position: N/A (disabled)
CPU: 2x Intel(R) Celeron(R) CPU N2840 @ 2.16GHz