Note Tag Editor: Capture back button

This way the tags are even updated with the back button.

lib/widgets/note_tag_editor.dart

@@ -34,7 +34,7 @@ class _NoteTagEditorState extends State<NoteTagEditor> {
   Widget build(BuildContext context) {
     var theme = Theme.of(context);
 
-    return Scaffold(
+    var s = Scaffold(
       appBar: AppBar(
         leading: IconButton(
           icon: const Icon(Icons.arrow_back),
@@ -54,6 +54,14 @@ class _NoteTagEditorState extends State<NoteTagEditor> {
       ),
       body: buildView(_textController.text),
     );
+
+    return WillPopScope(
+      onWillPop: () async {
+        Navigator.of(context).pop(_selectedTags);
+        return false;
+      },
+      child: s,
+    );
   }
 
   Widget buildView(String query) {