Schema Does Not Load With URI myproto:///schema.json

[hediet]

In some cases, schemas registered by jsonValidation are not picked up.

This works:

"jsonValidation": [
	{
		"fileMatch": "foo.json",
		"url": "myproto:///schema.json"
	}
]

This does not work, which is the actual bug:

"jsonValidation": [
	{
		"fileMatch": "foo.json",
		"url": "./randomSchema.json"
	},
	{
		"fileMatch": "foo.json",
		"url": "myproto:///schema.json"
	}
]

However, this works (notice someRandomNameThatMakesThisWork):

"jsonValidation": [
	{
		"fileMatch": "foo.json",
		"url": "./randomSchema.json"
	},
	{
		"fileMatch": "foo.json",
		"url": "myproto://someRandomNameThatMakesThisWork/schema2.json"
	}
]

This took an eternety to debug :/ (also, because source maps don't seem to work for the json language extension and debugging the JSON server without sources is very tricky)
It seems like when merging schemas, something goes wrong when one of the involved schemas does not have a root.
Also, I always run into

resolveErrors.push(l10n.t('Problems loading reference \'{0}\': {1}', loc, unresolvedSchema.errors[0]));

I'm fine with myproto:///schema.json not working, but then it should consistently not work and a nice error message should be printed somewhere.