Exceptions when trying to remove a registered JSON schema and disposing a model. Fixes Microsoft/monaco-editor#1254

package.json

@@ -20,7 +20,7 @@
   },
   "devDependencies": {
     "jsonc-parser": "^2.0.3",
-    "monaco-editor-core": "0.16.0",
+    "monaco-editor-core": "0.16.1",
     "monaco-languages": "1.7.0",
     "monaco-plugin-helpers": "^1.0.2",
     "requirejs": "^2.3.6",

src/languageFeatures.ts

@@ -103,7 +103,7 @@ export class DiagnosticsAdapter {
 			return worker.doValidation(resource.toString()).then(diagnostics => {
 				const markers = diagnostics.map(d => toDiagnostics(resource, d));
 				let model = monaco.editor.getModel(resource);
-				if (model.getModeId() === languageId) {
+				if (model && model.getModeId() === languageId) {
 					monaco.editor.setModelMarkers(model, languageId, markers);
 				}
 			});