pref: Return empty string for null or empty input

Author: HowieHz

src/main/java/top/howiehz/halo/plugin/extra/api/service/basic/post/render/pangu/impl/PanguSpacingServiceImpl.java

@@ -38,7 +38,7 @@ public PanguSpacingServiceImpl() {
     @Override
     public String applySpacingInHtml(String htmlContent) {
         if (htmlContent == null || htmlContent.isEmpty()) {
-            return htmlContent;
+            return "";
         }
 
         try {
@@ -72,7 +72,7 @@ public String applySpacingInHtml(Map<String, Object> params) {
 
         String htmlContent = htmlContentObj.toString();
         if (htmlContent.isEmpty()) {
-            return htmlContent;
+            return "";
         }
 
         // Extract selector (optional)
@@ -115,7 +115,7 @@ public String applySpacingInHtml(Map<String, Object> params) {
     @Override
     public String applySpacingInText(String text) {
         if (text == null || text.isEmpty()) {
-            return text;
+            return "";
         }
         try {
             return pangu.spacingText(text);

src/main/java/top/howiehz/halo/plugin/extra/api/service/js/post/render/shiki/ShikiRenderCodeService.java

@@ -239,7 +239,6 @@ public String renderCode(String content, ShikiConfig shikiConfig) {
 
         // 返回最终 HTML 内容，避免 Jsoup 自动格式化破坏原始结构（如多行 mermaid 代码无分号结尾时）
         doc.outputSettings(new Document.OutputSettings().prettyPrint(false));
-
         return doc.body().html();
     }