Exceptions when trying to remove a registered JSON schema and disposing a model

[foxable]

monaco-editor version: 0.15.6
Browser: Chrome
OS: Windows 10

I create instances of monaco-editor to edit several JSON configurations, each having a different, dynamically generated JSON schema. Since there may be a lot of different JSON schemas and the schema may change over time, I remove each schema from the JSON defaults whenever disposing the associated monaco instance (including the model). This to avoid unnecessary memory usage.

Unfortunately, this approach causes exceptions with monaco-editor 0.15.6. You can reproduce the issue with the following snippet:

var modelUri = monaco.Uri.parse("a://b/foo.json");
var model = monaco.editor.createModel("{}", "json", modelUri);

function setSchemas(newSchemas) {
    monaco.languages.json.jsonDefaults.setDiagnosticsOptions({
        schemas: newSchemas
    });
}

setSchemas([{
    uri: "http://myserver/foo-schema.json",
    fileMatch: [modelUri.toString()]
}]);

var editor = monaco.editor.create(document.getElementById("container"), {
    model: model
});

setTimeout(function() {
    setSchemas([]);
    model.dispose();
}, 1000);

This results in the following Exception: jsonMode.js:7 TypeError: Cannot read property 'getModeId' of null. Monaco tries to find the associated model by its URI, which fails and results in the null pointer.

I also tried to remove the JSON schema after disposing the model. However, this results in another exception, namely Uncaught (in promise) TypeError: Cannot read property 'withSyncedResources' of null. In this case, monaco tries to access the JSON worker, which was already stopped when disposing the model.

[nodejh]

I have the same issue on macOS Chrome.