Having a null 'uri' is valid.

packages/url_launcher/url_launcher_web/example/integration_test/link_widget_test.dart

@@ -83,6 +83,25 @@ void main() {
       expect(containerSize.width, 100.0);
       expect(containerSize.height, 100.0);
     });
+
+    // See: https://github.com/flutter/plugins/pull/3522#discussion_r574703724
+    testWidgets('uri can be null', (WidgetTester tester) async {
+      await tester.pumpWidget(Directionality(
+        textDirection: TextDirection.ltr,
+        child: WebLinkDelegate(TestLinkInfo(
+          uri: null,
+          target: LinkTarget.defaultTarget,
+          builder: (BuildContext context, FollowLink? followLink) {
+            return Container(width: 100, height: 100);
+          },
+        )),
+      ));
+      // Platform view creation happens asynchronously.
+      await tester.pumpAndSettle();
+
+      final html.Element anchor = _findSingleAnchor();
+      expect(anchor.hasAttribute('href'), false);
+    });
   });
 }
 
@@ -115,7 +134,7 @@ class TestLinkInfo extends LinkInfo {
   final LinkWidgetBuilder builder;
 
   @override
-  final Uri uri;
+  final Uri? uri;
 
   @override
   final LinkTarget target;

packages/url_launcher/url_launcher_web/lib/src/link.dart

@@ -51,7 +51,7 @@ class WebLinkDelegateState extends State<WebLinkDelegate> {
   void didUpdateWidget(WebLinkDelegate oldWidget) {
     super.didUpdateWidget(oldWidget);
     if (widget.link.uri != oldWidget.link.uri) {
-      _controller.setUri(widget.link.uri!);
+      _controller.setUri(widget.link.uri);
     }
     if (widget.link.target != oldWidget.link.target) {
       _controller.setTarget(widget.link.target);
@@ -78,7 +78,7 @@ class WebLinkDelegateState extends State<WebLinkDelegate> {
             onCreatePlatformView: (PlatformViewCreationParams params) {
               _controller = LinkViewController.fromParams(params, context);
               return _controller
-                ..setUri(widget.link.uri!)
+                ..setUri(widget.link.uri)
                 ..setTarget(widget.link.target);
             },
             surfaceFactory:
@@ -193,7 +193,7 @@ class LinkViewController extends PlatformViewController {
       return;
     }
 
-    if (_uri.hasScheme) {
+    if (_uri != null && _uri!.hasScheme) {
       // External links will be handled by the browser, so we don't have to do
       // anything.
       return;
@@ -207,10 +207,12 @@ class LinkViewController extends PlatformViewController {
     pushRouteNameToFramework(context, routeName);
   }
 
-  late Uri _uri;
+  Uri? _uri;
 
   /// Set the [Uri] value for this link.
-  void setUri(Uri uri) {
+  ///
+  /// When Uri is null, the `href` attribute of the link is removed.
+  void setUri(Uri? uri) {
     assert(_isInitialized);
     _uri = uri;
     if (uri == null) {