editor: disallow inserting empty embed urls/code

Signed-off-by: 01zulfi <85733202+01zulfi@users.noreply.github.com>

packages/editor/src/toolbar/popups/embed-popup.tsx

@@ -73,6 +73,7 @@ export function EmbedPopup(props: EmbedPopupProps) {
       onClose={() => onClose()}
       action={{
         title: strings.save(),
+        disabled: src.trim() === "",
         onClick: () => {
           setError(null);
           let _src = src;