dialog: Support suggested-action dialog with title only, no message

Author: chrisbobbe

lib/widgets/dialog.dart

@@ -145,7 +145,7 @@ DialogStatus<void> showErrorDialog({
 DialogStatus<bool> showSuggestedActionDialog({
   required BuildContext context,
   required String title,
-  required String message,
+  String? message,
   required String? actionButtonText,
   bool destructiveActionButton = false,
 }) {
@@ -154,7 +154,7 @@ DialogStatus<bool> showSuggestedActionDialog({
     context: context,
     builder: (BuildContext context) => AlertDialog.adaptive(
       title: Text(title),
-      content: _adaptiveContent(Text(message)),
+      content: message != null ? _adaptiveContent(Text(message)) : null,
       actions: [
         _adaptiveAction(
           onPressed: () => Navigator.pop<bool>(context, null),

test/widgets/dialog_checks.dart

@@ -109,7 +109,7 @@ void checkNoDialog(WidgetTester tester) {
 /// Tap the action button by calling `tester.tap(find.byWidget(actionButton))`.
 (Widget, Widget) checkSuggestedActionDialog(WidgetTester tester, {
   required String expectedTitle,
-  required String expectedMessage,
+  String? expectedMessage,
   String? expectedActionButtonText,
   bool expectDestructiveActionButton = false,
 }) {
@@ -121,8 +121,10 @@ void checkNoDialog(WidgetTester tester) {
       final dialog = tester.widget<AlertDialog>(find.bySubtype<AlertDialog>());
       tester.widget(find.descendant(matchRoot: true,
         of: find.byWidget(dialog.title!), matching: find.text(expectedTitle)));
-      tester.widget(find.descendant(matchRoot: true,
-        of: find.byWidget(dialog.content!), matching: find.text(expectedMessage)));
+      if (expectedMessage != null) {
+        tester.widget(find.descendant(matchRoot: true,
+          of: find.byWidget(dialog.content!), matching: find.text(expectedMessage)));
+      }
 
       final actionButton = tester.widget(find.descendant(of: find.byWidget(dialog),
         matching: find.widgetWithText(TextButton, expectedActionButtonText ?? 'Continue')));
@@ -135,8 +137,10 @@ void checkNoDialog(WidgetTester tester) {
       final dialog = tester.widget<CupertinoAlertDialog>(find.byType(CupertinoAlertDialog));
       tester.widget(find.descendant(matchRoot: true,
         of: find.byWidget(dialog.title!), matching: find.text(expectedTitle)));
-      tester.widget(find.descendant(matchRoot: true,
-        of: find.byWidget(dialog.content!), matching: find.text(expectedMessage)));
+      if (expectedMessage != null) {
+        tester.widget(find.descendant(matchRoot: true,
+          of: find.byWidget(dialog.content!), matching: find.text(expectedMessage)));
+      }
 
       final actionButton = tester.widget<CupertinoDialogAction>(
         find.descendant(