nmtui: fix WireGuard peer editor empty fields

Previously, input fields for peer attributes such as 'Public Key' were
not pre-populated with the existing settings of the peer. This was due
to the WireGuard peer editor class not setting its peer property during
object construction, as the necessary flag was absent. This commit
addresses and fixes this issue.

Closes #1443

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1851

src/nmtui/nmt-wireguard-peer-editor.c

@@ -237,11 +237,12 @@ nmt_wireguard_peer_editor_class_init(NmtWireguardPeerEditorClass *peer_class)
      *
      * The page's #NMWireGuardPeer.
      */
-    g_object_class_install_property(object_class,
+    g_object_class_install_property(
+        object_class,
         PROP_PEER,
         g_param_spec_boxed("peer",
                            "",
                            "",
                            nm_wireguard_peer_get_type(),
-                                                       G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+                           G_PARAM_READWRITE | G_PARAM_CONSTRUCT | G_PARAM_STATIC_STRINGS));
 }