[MC-123756] Trying to load broken resource pack also disables all intact resource packs ("Caught error stitching, removing all assigned resourcepacks")

The bug

I loaded a resource pack containing a json model. This model uses a texture whose name contains uppercase letters (see picture attached). Whether this texture exists or not does not matter, the uppercase letters in the json file resulted in multiple errors (see log above).
Finally, minecraft did not load the resource pack, but the default assets were not loaded (see pictures attached).

Workaround

A simple reload(F3 + T) lets the default assets appear.
Changing the uppercase letters to lowercase makes the use of the resource pack possible again.

Steps to reproduce

Load the attached XtraPack.zip

[...]
21:09:45	dfb	Unable to load model: 'minecraft:item/pickaxe' referenced from: minecraft:iron_pickaxe#inventory: java.io.FileNotFoundException: minecraft:models/item/pickaxe.json
21:09:45	cfs	Caught error stitching, removing all assigned resourcepacks
i: Non [a-z0-9/._-] character in path of location: minecraft:halb/leggings/item (1)
	at pc.<init>(SourceFile:38)
	at pc.<init>(SourceFile:43)
	at cvb.a(SourceFile:200)
	at cvb$$Lambda$937/2015935595.accept(Unknown Source)
	at java.util.ArrayList.forEach(ArrayList.java:1249)
	at cvb.a(SourceFile:200)
	at cvb.a(SourceFile:196)
	at cvb$$Lambda$935/876084303.accept(Unknown Source)
	at java.util.ArrayList.forEach(ArrayList.java:1249)
	at cvb.a(SourceFile:191)
	at dfb.a(SourceFile:336)
	at dfb$$Lambda$931/1985894997.apply(Unknown Source)
	at java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:267)
	at java.util.HashMap$ValueSpliterator.forEachRemaining(HashMap.java:1612)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:512)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:502)
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
	at dfb.a(SourceFile:336)
	at dfc.a(SourceFile:24)
	at vh.c(SourceFile:124)
	at vh.a(SourceFile:107)
	at cfs.f(SourceFile:684)
	at cmo$2.a(SourceFile:65)
	at cgt.mouseClicked(SourceFile:103)
	at chp.mouseClicked(SourceFile:46)
	at cfu.b(SourceFile:83)
	at cfu$$Lambda$1007/1191848005.run(Unknown Source)
	at ckc.a(SourceFile:430)
	at cfu.a(SourceFile:83)
	at cfu$$Lambda$838/41975027.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.glfwWaitEventsTimeout(GLFW.java:3108)
	at cgc.a(SourceFile:321)
	at cfs.c(SourceFile:875)
	at cfs.a(SourceFile:395)
	at net.minecraft.client.main.Main.main(SourceFile:144)
21:09:45	vh	Reloading ResourceManager: Default

A simple reload(F3 + T) lets the default assets appear.
Changing the uppercase letters to lowercase makes the use of the resource pack possible again.

Steps to reproduce

Load the attached XtraPack.zip