Fixed slash menu attempting to execute item when there are no items (#368)

Author: matthewlipski

packages/core/src/shared/plugins/suggestion/SuggestionPlugin.ts

@@ -346,6 +346,10 @@ export const setupSuggestionsMenu = <
 
           // Selects an item and closes the menu.
           if (event.key === "Enter") {
+            if (items.length === 0) {
+              return true;
+            }
+
             deactivate(view);
             editor._tiptapEditor
               .chain()