[MC-183779] NPE Bootstrap Exception 20w19a -> 20w20a

Upgrading a 20w19a server to 20w20a, the following exception occurs:

[16:29:51] [main/ERROR]: Unable to bootstrap registry 'minecraft:entity_type'
[16:29:51] [main/ERROR]: Unable to bootstrap registry 'minecraft:feature'
Exception in thread "main" java.lang.ExceptionInInitializerError
	at gl.H(SourceFile:94)
	at gl.a(SourceFile:132)
	at java.base/java.util.LinkedHashMap$LinkedEntrySet.forEach(LinkedHashMap.java:671)
	at gl.<clinit>(SourceFile:131)
	at aoc.a(SourceFile:144)
	at aoc.<clinit>(SourceFile:150)
	at ckx.<clinit>(SourceFile:23)
	at cka.<clinit>(SourceFile:64)
	at cqg.<clinit>(SourceFile:77)
	at cif.<clinit>(SourceFile:64)
	at net.minecraft.server.MinecraftServer.<clinit>(SourceFile:179)
Caused by: java.lang.NullPointerException
	at bsh.<init>(SourceFile:44)
	at bqk.<clinit>(SourceFile:9)
	... 11 more

Downgrading the server to 20w19a fixes the issue. I'd happily provide the map or additional debug information if needed.