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/misleading-screenshot/backend.js

@@ -0,0 +1,3 @@
+export default {
+	hooks: {},
+};

packages/marketplace/tests/fixtures/audit/misleading-screenshot/expected.json

@@ -0,0 +1,7 @@
+{
+	"verdict": "pass",
+	"maxRiskScore": 0,
+	"categories": [],
+	"images": "warn",
+	"imageCategories": ["misleading"]
+}

packages/marketplace/tests/fixtures/audit/misleading-screenshot/manifest.json

@@ -0,0 +1,10 @@
+{
+	"id": "admin-helper",
+	"version": "1.0.0",
+	"capabilities": ["admin:panel"],
+	"allowedHosts": [],
+	"storage": {},
+	"hooks": [],
+	"routes": [],
+	"admin": {}
+}