added error handling for invalid urls

lib/service/url_launcher.dart

@@ -1,8 +1,14 @@
 import 'package:url_launcher/url_launcher.dart';
 
-Future<void> launchUrlFromString(String url) async {
-  final Uri uri = Uri.parse(url);
+Future<UrlLaunchErrorCode> launchUrlFromString(String url) async {
+  final Uri? uri = Uri.tryParse(url);
+  final isValid =
+      uri != null && uri.hasAbsolutePath && uri.scheme.startsWith('http');
+  if (!isValid) return UrlLaunchErrorCode.invalidUrl;
   if (!await launchUrl(uri, mode: LaunchMode.externalApplication)) {
-    throw Exception('Could not launch $url');
+    return UrlLaunchErrorCode.couldNotLaunch;
   }
+  return UrlLaunchErrorCode.none;
 }
+
+enum UrlLaunchErrorCode { none, couldNotLaunch, invalidUrl }