Fix issue with previewing certain pages (#1571)

* Fix previewing pages when page attributes are set

tests/admin/test_pages.py

@@ -0,0 +1,26 @@
+from tests.helpers import create_ctfd, destroy_ctfd, login_as_user
+
+
+def test_previewing_pages_works():
+    """Test that pages can be previewed properly"""
+    app = create_ctfd()
+    with app.app_context():
+        client = login_as_user(app, name="admin", password="password")
+
+        with client.session_transaction() as sess:
+            data = {
+                "title": "title",
+                "route": "route",
+                "content": "content_testing",
+                "nonce": sess.get("nonce"),
+                "draft": "y",
+                "hidden": "y",
+                "auth_required": "y",
+            }
+
+        r = client.post("/admin/pages/preview", data=data)
+        assert r.status_code == 200
+        resp = r.get_data(as_text=True)
+        assert "content_testing" in resp
+
+    destroy_ctfd(app)