fix to update state of defintion button in toolbar

lib/pangea/widgets/chat/message_text_selection.dart

@@ -1,12 +1,13 @@
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';
-import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 
 class MessageTextSelection {
   String? selectedText;
   String messageText = "";
+  final StreamController<String?> selectionStream =
+      StreamController<String?>.broadcast();
 
   void setMessageText(String text) {
     messageText = text;
@@ -21,7 +22,7 @@ class MessageTextSelection {
     if (BrowserContextMenu.enabled && kIsWeb) {
       BrowserContextMenu.disableContextMenu();
     }
-    // selectionStream.add(selectedText);
+    selectionStream.add(selectedText);
   }
 
   void clearTextSelection() {
@@ -29,6 +30,6 @@ class MessageTextSelection {
     if (kIsWeb && !BrowserContextMenu.enabled) {
       BrowserContextMenu.enableContextMenu();
     }
-    // selectionStream.add(selectedText);
+    selectionStream.add(selectedText);
   }
 }

lib/pangea/widgets/chat/message_toolbar.dart

@@ -141,6 +141,7 @@ class MessageToolbar extends StatefulWidget {
 class MessageToolbarState extends State<MessageToolbar> {
   Widget? child;
   MessageMode? _currentMode;
+  bool hasSelectedText = false;
   late StreamSubscription<String?> _selectionStream;
   late StreamSubscription<MessageMode> _toolbarModeStream;
 
@@ -233,9 +234,23 @@ class MessageToolbarState extends State<MessageToolbar> {
   @override
   void initState() {
     super.initState();
+    if (widget.textSelection.selectedText != null) {
+      hasSelectedText = true;
+    }
+
     _toolbarModeStream = widget.toolbarModeStream.stream.listen((mode) {
       updateMode(mode);
     });
+
+    _selectionStream =
+        widget.textSelection.selectionStream.stream.listen((value) {
+      final bool shouldSetState =
+          value != null && !hasSelectedText || value == null && hasSelectedText;
+      hasSelectedText = value != null;
+      if (shouldSetState) {
+        setState(() {});
+      }
+    });
   }
 
   @override