【综合】关闭文档，内存问题处理

PDF Office/PDF Master/Class/PDFWindowController/ViewController/KMMainViewController.swift

@@ -1880,7 +1880,7 @@ import Cocoa
         }
         self.removeAutoSaveInfo()
         KMAdsManager.defaultManager.dismissSheetModal(for: self.readContentView)
-        self.myDocument = nil
+//        self.myDocument = nil
     }
     
     public func clearSecureOptions() {