I have no Idea what happened, somehow when I opened the game I accidentally clicked somewhere I could not catch and it just crashed for unknown reasons. It is a mystery. The only thing I could catch is the crash report:

---- Minecraft Crash Report ----
// This doesn't make any sense!

Time: 11/20/18, 6:41 PM
Description: Rendering screen

java.lang.NoClassDefFoundError: net/minecraft/client/renderer/system/GlStateManager
at com.mojang.realmsclient.RealmsMainScreen.drawRealmsLogo(RealmsMainScreen.java:880)
at com.mojang.realmsclient.RealmsMainScreen.render(RealmsMainScreen.java:816)
at cpy.a(SourceFile:102)
at dbc.a(SourceFile:794)
at cmx.d(SourceFile:850)
at cmx.b(SourceFile:389)
at net.minecraft.client.main.Main.main(SourceFile:145)
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.renderer.system.GlStateManager
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:583)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:190)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:499)
... 7 more

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

– Head –
Thread: Client thread
Stacktrace:
at com.mojang.realmsclient.RealmsMainScreen.drawRealmsLogo(RealmsMainScreen.java:880)
at com.mojang.realmsclient.RealmsMainScreen.render(RealmsMainScreen.java:816)
at cpy.a(SourceFile:102)

– Screen render details –
Details:
Screen name: cpy
Mouse location: Scaled: (246, 149). Absolute: (738.000000, 448.000000)
Screen size: Scaled: (456, 256). Absolute: (1366, 768). Scale factor of 3.000000
Stacktrace:
at dbc.a(SourceFile:794)
at cmx.d(SourceFile:850)
at cmx.b(SourceFile:389)
at net.minecraft.client.main.Main.main(SourceFile:145)

– System Details –
Details:
Minecraft Version: 18w46a
Operating System: Linux (amd64) version 4.15.0-39-generic
Java Version: 10.0.2, Oracle Corporation
Java VM Version: OpenJDK 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 1013993968 bytes (967 MB) / 1375731712 bytes (1312 MB) up to 2147483648 bytes (2048 MB)
JVM Flags: 8 total; -Xss1M -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
Launched Version: 18w46a
LWJGL: 3.1.6 build 14
OpenGL: Mesa DRI Intel(R) HD Graphics 520 (Skylake GT2) GL version 3.0 Mesa 18.0.5, Intel Open Source Technology Center
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: vanilla, programer_art
Current Language: English (US)
CPU: 4x Intel(R) Core(TM) i5-6200U CPU @ 2.30GHz