neon: Allow empty scheme for login

packages/neon/lib/src/pages/login.dart

@@ -191,10 +191,18 @@ class _LoginPageState extends State<LoginPage> {
                                   hintText: 'https://...',
                                 ),
                                 initialValue: widget.serverURL,
-                                validator: (final input) => validateHttpUrl(context, input),
+                                validator: (final input) => validateHttpUrl(
+                                  context,
+                                  input,
+                                  allowEmptyScheme: true,
+                                ),
                                 onFieldSubmitted: (final input) {
                                   if (_formKey.currentState!.validate()) {
-                                    _loginBloc.setServerURL(input);
+                                    var url = input;
+                                    if (!(url.startsWith('http://') || url.startsWith('https://'))) {
+                                      url = 'http://$url';
+                                    }
+                                    _loginBloc.setServerURL(url);
                                   } else {
                                     _focusNode.requestFocus();
                                   }

packages/neon/lib/src/utils/validators.dart

@@ -4,21 +4,25 @@ String? validateHttpUrl(
   final BuildContext context,
   final String? input, {
   final bool httpsOnly = false,
+  final bool allowEmptyScheme = false,
 }) {
   if (input == null || input == '') {
     return AppLocalizations.of(context).errorInvalidURL;
   }
   try {
     final uri = Uri.parse(input);
-    // TODO: Maybe make a better error message for http URLs if only https is allowed
-    if (!(!httpsOnly && (uri.isScheme('http')) || uri.isScheme('https'))) {
-      return AppLocalizations.of(context).errorInvalidURL;
+    if (uri.isScheme('https')) {
+      return null;
     }
-  } catch (e) {
-    return AppLocalizations.of(context).errorInvalidURL;
+    if (uri.isScheme('http') && !httpsOnly) {
+      return null;
     }
+    if (uri.isScheme('') && allowEmptyScheme) {
       return null;
     }
+  } catch (_) {}
+  return AppLocalizations.of(context).errorInvalidURL;
+}
 
 String? validateNotEmpty(final BuildContext context, final String? input) {
   if (input == null || input == '') {