[Autofill Assistant] Do not store empty contact

Before, when an empty contact was selected, the delegate would send null
for name, phone and email. These empty datapoints were transformed into
an empty contact profile which was stored in |UserData|.
With this CL we will store nullptr if null was selected from the view.

This will help to not send an empty contact once we close the update
loop.

Bug: b/144005336
Change-Id: Ia883dc89bc83acd03cb12f7e7164fb31f38fdc50
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1929815
Commit-Queue: Sandro Maggi <sandromaggi@google.com>
Reviewed-by: Clemens Arbesser <arbesser@google.com>
Cr-Commit-Position: refs/heads/master@{#718110}

chrome/browser/android/autofill_assistant/assistant_collect_user_data_delegate.cc

@@ -53,6 +53,11 @@ void AssistantCollectUserDataDelegate::OnContactInfoChanged(
     const base::android::JavaParamRef<jstring>& jpayer_name,
     const base::android::JavaParamRef<jstring>& jpayer_phone,
     const base::android::JavaParamRef<jstring>& jpayer_email) {
+  if (!jpayer_name && !jpayer_phone && !jpayer_email) {
+    ui_controller_->OnContactInfoChanged(nullptr);
+    return;
+  }
+
   std::string name = SafeConvertJavaStringToNative(env, jpayer_name);
   std::string phone = SafeConvertJavaStringToNative(env, jpayer_phone);
   std::string email = SafeConvertJavaStringToNative(env, jpayer_email);