Crash when importing flat dimensions

The game crashes when I import a world setting file that has a flat world dimension.
If you remove the flat dimension (Line 130) the game proceeds to import the world settings.
I tried to check if the JSON is valid (it is) and if i made some errors while writing it but I cannot find anything.
I even tried to change dimension's settings (like "shrunk" etc.) but nothing changes

(20w21a) [^crash-2020-05-24_11.22.55-client.txt]

Description: mouseClicked event handler

java.lang.StringIndexOutOfBoundsException: String index out of range: -74
	at java.lang.String.substring(Unknown Source)
	at org.apache.commons.lang3.text.WordUtils.wrap(WordUtils.java:328)
	at org.apache.commons.lang3.text.WordUtils.wrap(WordUtils.java:176)
	at org.apache.commons.lang3.text.WordUtils.wrap(WordUtils.java:100)
	at dne.a(SourceFile:29)
	at dsu.a(SourceFile:174)
	at dlz.b(SourceFile:33)
	at dlt.a(SourceFile:16)
	at dlx.a(SourceFile:149)
	at dmw.a(SourceFile:27)
	at dkp.b(SourceFile:86)
	at dpg.a(SourceFile:429)
	at dkp.a(SourceFile:86)
	at dkp.c(SourceFile:150)
	at alz.execute(SourceFile:94)
	at dkp.b(SourceFile:150)
	at org.lwjgl.glfw.GLFWMouseButtonCallbackI.callback(GLFWMouseButtonCallbackI.java:36)
	at org.lwjgl.system.JNI.invokeV(Native Method)
	at org.lwjgl.glfw.GLFW.glfwPollEvents(GLFW.java:3101)
	at com.mojang.blaze3d.systems.RenderSystem.flipFrame(SourceFile:99)
	at dfq.e(SourceFile:301)
	at dko.e(SourceFile:1040)
	at dko.d(SourceFile:633)
	at net.minecraft.client.main.Main.main(SourceFile:208)