[MC-190010] The game crashes when using a mouse button to swap item in hands while inside of an inventory but not hovering over a slot

The game crashes, when using specific hotkeys to swap items in hands, when in inventory. However, the crash only seems to occur, when clicking anywhere on the screen, while not hovering over an item slot.

Affects 4th, 5th and middle mouse button and doesn't seem to affect any other hotkeys. => Could be related to ~~MC-188659~~.

Stack trace

1.16-pre6: [^crash-2020-06-16_13.42.59-client.txt]

Description: mouseClicked event handler

java.lang.NullPointerException: mouseClicked event handler
	at dro.a(SourceFile:382)
	at dro.a(SourceFile:369)
	at dsb.a(SourceFile:500)
	at dlz.b(SourceFile:92)
	at dlz$$Lambda$2870/719866697.run(Unknown Source)
	at dqt.a(SourceFile:431)
	at dlz.a(SourceFile:92)
	at dlz.c(SourceFile:162)
	at dlz$$Lambda$2869/1086330138.run(Unknown Source)
	at amn.execute(SourceFile:94)
	at dlz.b(SourceFile:162)
	at dlz$$Lambda$2220/892034876.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:3101)
	at com.mojang.blaze3d.systems.RenderSystem.flipFrame(SourceFile:109)
	at dgz.e(SourceFile:301)
	at dly.e(SourceFile:1041)
	at dly.d(SourceFile:654)
	at net.minecraft.client.main.Main.main(SourceFile:215)