Crash while F3 menu tries to access tags while /reload-ing

The bug

When you have the F3 menu open and you look at a block which is listed in block tags and you /reload datapacks, there's a chance the game crashes. The more tags there are, the higher the probability.
The attached world has a datapack with 100 block tags. Every block tag contains all blocks.

How to reproduce

• Open the attached world with (both vanilla and) the MC-151346 datapack enabled.

• Open the F3 menu and look at any block (all the blocks are included in the tags).

• Now type /reload every time it finished reloading --> after a few attempts the game crashes

Crash report

1.14.1 Pre-Release 2\: [^crash-2019-05-09_22.41.55-client.txt]

Description: Unexpected error

java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextNode(HashMap.java:1429)
	at java.util.HashMap$EntryIterator.next(HashMap.java:1463)
	at java.util.HashMap$EntryIterator.next(HashMap.java:1461)
	at zc.a(SourceFile:77)
	at cwv.f(SourceFile:367)
	at cwv.d(SourceFile:146)
	at cwv.b(SourceFile:99)
	at cwd.a(SourceFile:256)
	at dkk.a(SourceFile:657)
	at cvk.e(SourceFile:954)
	at cvk.b(SourceFile:411)
	at net.minecraft.client.main.Main.main(SourceFile:154)


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

-- Head --
Thread: Client thread
Stacktrace:
	at java.util.HashMap$HashIterator.nextNode(HashMap.java:1429)
	at java.util.HashMap$EntryIterator.next(HashMap.java:1463)
	at java.util.HashMap$EntryIterator.next(HashMap.java:1461)
	at zc.a(SourceFile:77)
	at cwv.f(SourceFile:367)
	at cwv.d(SourceFile:146)
	at cwv.b(SourceFile:99)
	at cwd.a(SourceFile:256)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [djx['AlexCubed'/1, l='MpServer', x=7.79, y=4.00, z=10.05]]
	Chunk stats: MultiplayerChunkCache: 729, 441
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: {}
	Level spawn location: World: (0,4,0), Chunk: (at 0,0,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 3000 game time, 3000 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: false
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at dhn.a(SourceFile:421)
	at cvk.b(SourceFile:1923)
	at cvk.b(SourceFile:431)
	at net.minecraft.client.main.Main.main(SourceFile:154)

-- System Details --
Details:
	Minecraft Version: 1.14.1 Pre-Release 2
	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: 997923824 bytes (951 MB) / 1912602624 bytes (1824 MB) up to 2147483648 bytes (2048 MB)
	JVM Flags: 9 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xss1M -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
	Launched Version: 1.14.1 Pre-Release 2
	LWJGL: 3.2.1 build 12
	OpenGL: GeForce GTX 1060/PCIe/SSE2 GL version 4.6.0 NVIDIA 430.39, 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 (US)
	CPU: 12x Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz