Crash when putting spaces and clicking on "Done" in the jigsaw GUI

18w46a: [^crash-2018-11-15_18.02.13-client.txt]

Description: mouseClicked event handler

j: Non [a-z0-9/._-] character in path of location: minecraft:empty 
	at px.<init>(SourceFile:38)
	at px.<init>(SourceFile:43)
	at csp.j(SourceFile:51)
	at csp.h(SourceFile:42)
	at csp.a(SourceFile:16)
	at csp$1.a(SourceFile:65)
	at cnu.mouseClicked(SourceFile:103)
	at cor.mouseClicked(SourceFile:46)
	at csp.mouseClicked(SourceFile:116)
	at cmy.b(SourceFile:84)
	at cmy$$Lambda$1240/1673896541.run(Unknown Source)
	at crc.a(SourceFile:430)
	at cmy.a(SourceFile:84)
	at cmy$$Lambda$1068/2123685471.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.glfwPollEvents(GLFW.java:3029)
	at com.mojang.blaze3d.platform.GLX.pollEvents(SourceFile:223)
	at cmx.d(SourceFile:830)
	at cmx.b(SourceFile:389)
	at net.minecraft.client.main.Main.main(SourceFile:145)

How to reproduce

1. Get a jigsaw block (/give @s minecraft:jigsaw)

2. Open the GUI

3. Write some spaces on any row

4. Click on "Done"

5. Well done, it crashed!