Crash while creating a customized superflat world using capital letters

How to reproduce:

Please, follow this steps:

1. Create New World.

2. More world options.

3. World type: Superflat

4. Customise.

5. Remove ALL the layers.

6. Presets.

7. Write with CAPITAL LETTERS the name of a block, for example: MINECRAFT:BEDROCK.

The game will crash.

Here is the crash report:

---- Minecraft Crash Report ----
// Oops.Time: 28/06/18 21:54
Description: mouseClicked event handleri: Non [a-z0-9_.-] character in namespace of location: MINECRAFT:BEDROCK
	at ox.<init>(SourceFile:35)
	at ox.<init>(SourceFile:43)
	at bbr.a(SourceFile:136)
	at btb.a(SourceFile:256)
	at btb.b(SourceFile:272)
	at btb.a(SourceFile:337)
	at chp.a(SourceFile:70)
	at cid$1.a(SourceFile:170)
	at cfq.mouseClicked(SourceFile:103)
	at cgm.mouseClicked(SourceFile:46)
	at cer.b(SourceFile:67)
	at cer$$Lambda$883/1930186237.run(Unknown Source)
	at cig.a(SourceFile:430)
	at cer.a(SourceFile:67)
	at cer$$Lambda$753/2002232191.invoke(Unknown Source)
	at org.lwjgl.glfw.GLFWMouseButtonCallbackI.callback(GLFWMouseButtonCallbackI.java:36)
	at org.lwjgl.system.JNI.invokeV(Native Method)
	at org.lwjgl.glfw.GLFW.glfwWaitEventsTimeout(GLFW.java:3108)
	at cez.a(SourceFile:317)
	at cep.c(SourceFile:833)
	at cep.a(SourceFile:373)
	at net.minecraft.client.main.Main.main(SourceFile:143)
A detailed walkthrough of the error, its code path and all known details is as follows:
----------------------------------------------------------------------------------------- Head --
Thread: Client thread
Stacktrace:
	at ox.<init>(SourceFile:35)
	at ox.<init>(SourceFile:43)
	at bbr.a(SourceFile:136)
	at btb.a(SourceFile:256)
	at btb.b(SourceFile:272)
	at btb.a(SourceFile:337)
	at chp.a(SourceFile:70)
	at cid$1.a(SourceFile:170)
	at cfq.mouseClicked(SourceFile:103)
	at cgm.mouseClicked(SourceFile:46)
	at cer.b(SourceFile:67)
	at cer$$Lambda$883/1930186237.run(Unknown Source)-- Affected screen --
Details:
	Screen name: cid
Stacktrace:
	at cig.a(SourceFile:430)
	at cer.a(SourceFile:67)
	at cer$$Lambda$753/2002232191.invoke(Unknown Source)
	at org.lwjgl.glfw.GLFWMouseButtonCallbackI.callback(GLFWMouseButtonCallbackI.java:36)
	at org.lwjgl.system.JNI.invokeV(Native Method)
	at org.lwjgl.glfw.GLFW.glfwWaitEventsTimeout(GLFW.java:3108)
	at cez.a(SourceFile:317)
	at cep.c(SourceFile:833)
	at cep.a(SourceFile:373)
	at net.minecraft.client.main.Main.main(SourceFile:143)-- System Details --
Details:
	Minecraft Version: 1.13-pre5
	Operating System: Windows 10 (amd64) version 10.0
	Java Version: 1.8.0_51, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 214100176 bytes (204 MB) / 788529152 bytes (752 MB) up to 1073741824 bytes (1024 MB)
	JVM Flags: 9 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xss1M -Xmx1G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=16M
	Launched Version: 1.13-pre5
	LWJGL: 3.1.6 build 14
	OpenGL: GeForce GTX 750 Ti/PCIe/SSE2 GL version 4.6.0 NVIDIA 388.13, NVIDIA Corporation
	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: 
	Current Language: English (United Kingdom)
	Profiler Position: N/A (disabled)
	CPU: 8x Intel(R) Core(TM) i7 CPU 920 @ 2.67GHz