Fix empty textspan with spell out crashes (#88738)

packages/flutter/lib/src/painting/text_span.dart

@@ -371,13 +371,14 @@ class TextSpan extends InlineSpan implements HitTestTarget, MouseTrackerAnnotati
     final bool effectiveSpellOut = spellOut ?? inheritedSpellOut;
 
     if (text != null) {
+      final int textLength = semanticsLabel?.length ?? text!.length;
       collector.add(InlineSpanSemanticsInformation(
         text!,
         stringAttributes: <ui.StringAttribute>[
-          if (effectiveSpellOut)
-            ui.SpellOutStringAttribute(range: TextRange(start: 0, end: semanticsLabel?.length ?? text!.length)),
-          if (effectiveLocale != null)
-            ui.LocaleStringAttribute(locale: effectiveLocale, range: TextRange(start: 0, end: semanticsLabel?.length ?? text!.length)),
+          if (effectiveSpellOut && textLength > 0)
+            ui.SpellOutStringAttribute(range: TextRange(start: 0, end: textLength)),
+          if (effectiveLocale != null && textLength > 0)
+            ui.LocaleStringAttribute(locale: effectiveLocale, range: TextRange(start: 0, end: textLength)),
         ],
         semanticsLabel: semanticsLabel,
         recognizer: recognizer,

packages/flutter/test/rendering/paragraph_test.dart

@@ -749,6 +749,18 @@ void main() {
     paragraph.assembleSemanticsNode(SemanticsNode(), SemanticsConfiguration(), <SemanticsNode>[]);
   });
 
+  test('Supports empty text span with spell out', () {
+    final RenderParagraph paragraph = RenderParagraph(
+      const TextSpan(text: '', spellOut: true),
+      textDirection: TextDirection.rtl,
+    );
+    layout(paragraph);
+    final SemanticsNode node = SemanticsNode();
+    paragraph.assembleSemanticsNode(node, SemanticsConfiguration(), <SemanticsNode>[]);
+    expect(node.attributedLabel.string, '');
+    expect(node.attributedLabel.attributes.length, 0);
+  });
+
   test('Asserts on unsupported gesture recognizer', () {
     final RenderParagraph paragraph = RenderParagraph(
       TextSpan(text: _kText, children: <InlineSpan>[