Show error screen when project cannot be loaded

src/lib/project-fetcher-hoc.jsx

@@ -66,6 +66,10 @@ const ProjectFetcherHOC = function (WrappedComponent) {
                 .then(projectAsset => {
                     if (projectAsset) {
                         this.props.onFetchedProjectData(projectAsset.data, loadingState);
+                    } else {
+                        // Treat failure to load as an error
+                        // Throw to be caught by catch later on
+                        throw new Error('Could not find project');
                     }
                 })
                 .then(() => {

test/integration/project-loading.test.js

@@ -47,6 +47,11 @@ describe('Loading scratch gui', () => {
             await expect(logs).toEqual([]);
         });
 
+        test('Nonexistent projects show error screen', async () => {
+            await loadUri(`${uri}#999999999999999999999`);
+            await clickText('Oops! Something went wrong.');
+        });
+
         test('Invalid url when loading project through modal lets you try again', async () => {
             await loadUri(uri);
             await clickText('View 2.0 Project');