Emdash source with visual editor image upload fix

Fixes:
1. media.ts: wrap placeholder generation in try-catch
2. toolbar.ts: check r.ok, display error message in popover

packages/blocks/vitest.config.ts

@@ -0,0 +1,9 @@
+import react from "@vitejs/plugin-react";
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+	plugins: [react()],
+	test: {
+		environment: "jsdom",
+	},
+});