update content-service/disk DiskFileController#getPreviewFile

content/content-service/src/main/java/cn/reghao/tnb/content/app/disk/controller/DiskFileController.java

@@ -74,7 +74,11 @@ public class DiskFileController {
     @GetMapping(value = "/preview", produces = MediaType.APPLICATION_JSON_VALUE)
     public String getPreviewFile(@RequestParam("fileId") String fileId) {
         DiskFileDetail diskFileDetail = diskFileService.getDiskFileDetail(fileId);
-        return WebResult.success(diskFileDetail);
+        if (diskFileDetail != null) {
+            return WebResult.success(diskFileDetail);
+        }
+
+        return WebResult.failWithMsg("获取文件详情失败");
     }
 
     @Operation(summary = "重命名文件", description = "N")