翻转""为equals调用方，防止空指针异常

ruoyi/src/main/java/com/ruoyi/common/utils/http/HttpUtils.java

@@ -204,7 +204,7 @@ public class HttpUtils
             String ret = "";
             while ((ret = br.readLine()) != null)
             {
-                if (ret != null && !ret.trim().equals(""))
+                if (ret != null && !"".equals(ret.trim()))
                 {
                     result.append(new String(ret.getBytes("ISO-8859-1"), "utf-8"));
                 }