Soft-lock on world loading with a data pack

Current Behaviour

When loading a world with a invalid data pack the game soft-locks and continues trying to load the world forever.

Post 1.13 Pre-release 6

The entire game crashes.

Expected behaviour

The world loads without the data pack (as /reload does) and prompt a message.

Description: Exception in server tick loop

i: Non [a-z0-9_.-] character in namespace of location: #minecraft:logs
	at on.<init>(SourceFile:35)
	at on.<init>(SourceFile:43)
	at ayu.a(SourceFile:166)
	at ayu.b(SourceFile:148)
	at ayu$$Lambda$1315/1900488066.apply(Unknown Source)
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
	at java.util.ArrayList$Itr.forEachRemaining(ArrayList.java:891)
	at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:512)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:502)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:576)
	at java.util.stream.AbstractPipeline.evaluateToArrayNode(AbstractPipeline.java:255)
	at java.util.stream.ReferencePipeline.toArray(ReferencePipeline.java:438)
	at ayu.<init>(SourceFile:41)