fix: compatible email are empty when comment notification triggered (#4685)

#### What type of PR is this?
/kind bug
/area core
/milestone 2.10.x

#### What this PR does / why we need it:
修复当评论或回复者的邮箱为空时通知报错的问题

#### Which issue(s) this PR fixes:
Fixes #4684

#### Does this PR introduce a user-facing change?
```release-note
修复当评论或回复者的邮箱为空时通知报错的问题

```

application/src/main/java/run/halo/app/content/comment/ReplyNotificationSubscriptionHelper.java

@@ -1,6 +1,8 @@
 package run.halo.app.content.comment;
 
+import io.micrometer.common.util.StringUtils;
 import lombok.RequiredArgsConstructor;
+import org.springframework.lang.Nullable;
 import org.springframework.stereotype.Component;
 import run.halo.app.content.NotificationReasonConst;
 import run.halo.app.core.extension.content.Comment;
@@ -56,13 +58,21 @@ public class ReplyNotificationSubscriptionHelper {
     void subscribeReply(Subscription.ReasonSubject reasonSubject,
         Identity identity) {
         var subscriber = createSubscriber(identity);
+        if (subscriber == null) {
+            return;
+        }
         var interestReason = new Subscription.InterestReason();
         interestReason.setReasonType(NotificationReasonConst.SOMEONE_REPLIED_TO_YOU);
         interestReason.setSubject(reasonSubject);
         notificationCenter.subscribe(subscriber, interestReason).block();
     }
 
+    @Nullable
     private Subscription.Subscriber createSubscriber(Identity author) {
+        if (StringUtils.isBlank(author.name())) {
+            return null;
+        }
+
         Subscription.Subscriber subscriber;
         if (author.isEmail()) {
             subscriber = subscriberEmailResolver.ofEmail(author.name());

application/src/main/java/run/halo/app/notification/EmailNotifier.java

@@ -43,6 +43,11 @@ public class EmailNotifier implements ReactiveNotifier {
         var emailSenderConfig =
             JsonUtils.DEFAULT_JSON_MAPPER.convertValue(senderConfig, EmailSenderConfig.class);
 
+        if (!emailSenderConfig.isEnable()) {
+            log.debug("Email notifier is disabled, skip sending email.");
+            return Mono.empty();
+        }
+
         JavaMailSenderImpl javaMailSender = getJavaMailSender(emailSenderConfig);
 
         String recipient = context.getMessage().getRecipient();
@@ -51,6 +56,11 @@ public class EmailNotifier implements ReactiveNotifier {
         var payload = context.getMessage().getPayload();
         return subscriberEmailResolver.resolve(subscriber)
             .flatMap(toEmail -> {
+                if (StringUtils.isBlank(toEmail)) {
+                    log.debug("Cannot resolve email for subscriber: [{}], skip sending email.",
+                        subscriber);
+                    return Mono.empty();
+                }
                 var htmlMono = appendHtmlBodyFooter(payload.getAttributes())
                     .doOnNext(footer -> {
                         if (StringUtils.isNotBlank(payload.getHtmlBody())) {
@@ -138,6 +148,7 @@ public class EmailNotifier implements ReactiveNotifier {
 
     @Data
     static class EmailSenderConfig {
+        private boolean enable;
         private String displayName;
         private String username;
         private String password;

application/src/main/resources/extensions/notification.yaml

@@ -19,22 +19,31 @@ spec:
     - group: sender
       label: 发件设置
       formSchema:
+        - $formkit: checkbox
+          label: "启用邮件通知器"
+          value: false
+          name: enable
         - $formkit: text
+          if: "$enable"
           label: "用户名"
           name: username
           validation: required
         - $formkit: password
+          if: "$enable"
           label: "密码"
           name: password
           validation: required
         - $formkit: text
+          if: "$enable"
           label: "显示名称"
           name: displayName
         - $formkit: text
+          if: "$enable"
           label: "SMTP 服务器地址"
           name: host
           validation: required
         - $formkit: text
+          if: "$enable"
           label: "端口号"
           name: port
           validation: required