修复删除下载项时内建下载器崩溃的bug

src/DownKyi/Services/Download/BuiltinDownloadService.cs

@@ -134,6 +134,8 @@ namespace DownKyi.Services.Download
             }
 
             // 开始下载
+            try
+            {
                 var downloadStatus = DownloadByBuiltin(downloading, urls, path, fileName);
                 if (downloadStatus)
                 {
@@ -146,6 +148,14 @@ namespace DownKyi.Services.Download
                     return nullMark;
                 }
             }
+            catch (FileNotFoundException e)
+            {
+                Core.Utils.Debugging.Console.PrintLine("BuiltinDownloadService.DownloadVideo()发生异常: {0}", e);
+                LogManager.Error("BuiltinDownloadService.DownloadVideo()", e);
+
+                return nullMark;
+            }
+        }
 
         #endregion