fix: hide zap button for profiles with no lud16

lib/widgets/chat_modal.dart

@@ -54,10 +54,13 @@ class _ChatModalWidget extends State<ChatModalWidget> {
                     }),
                 icon: Icon(Icons.mood),
               ),
+              if (widget.profile.lud16?.isNotEmpty ?? false)
                 IconButton.filled(
                   color: ZAP_1,
                   style: ButtonStyle(
-                  backgroundColor: WidgetStateColor.resolveWith((_) => LAYER_3),
+                    backgroundColor: WidgetStateColor.resolveWith(
+                      (_) => LAYER_3,
+                    ),
                   ),
                   onPressed: () {
                     Navigator.pop(context);