Put call to forget finished downloads in an else statement to prevent potential bugs

app/src/main/java/us/shandian/giga/ui/adapter/MissionAdapter.java

@@ -566,8 +566,9 @@ public class MissionAdapter extends Adapter<ViewHolder> implements Handler.Callb
                     mContext.sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, mission.storage.getUri()));
                 }
             }
+        } else if (!delete) {
+            mDownloadManager.forgetFinishedDownloads();
         }
-        mDownloadManager.forgetFinishedDownloads();
         applyChanges();
     }