Fix BrowserAccessibilityManagerMac: set empty selected text range.

content/browser/accessibility/browser_accessibility_manager_mac.mm

Index: content/browser/accessibility/browser_accessibility_manager_mac.mm
diff --git a/content/browser/accessibility/browser_accessibility_manager_mac.mm b/content/browser/accessibility/browser_accessibility_manager_mac.mm
index 604e42008faa45669f06517fad947ed8f2c832f0..b2dff5cf91602e237a02682f2ad1f5baf62a74f6 100644
--- a/content/browser/accessibility/browser_accessibility_manager_mac.mm
+++ b/content/browser/accessibility/browser_accessibility_manager_mac.mm
@@ -425,10 +425,14 @@ NSDictionary* BrowserAccessibilityManagerMac::
     focus_object = focus_object->GetClosestPlatformObject();
     auto native_focus_object = ToBrowserAccessibilityCocoa(focus_object);
     if (native_focus_object && [native_focus_object instanceActive]) {
-      [user_info setObject:[native_focus_object selectedTextMarkerRange]
-                    forKey:NSAccessibilitySelectedTextMarkerRangeAttribute];
       [user_info setObject:native_focus_object
                     forKey:NSAccessibilityTextChangeElement];
+
+      id selected_text = [native_focus_object selectedTextMarkerRange];
+      if (selected_text) {
+        [user_info setObject:selected_text
+                      forKey:NSAccessibilitySelectedTextMarkerRangeAttribute];
+      }
     }
   }