fix: the null pointer reference vulnerability

Fix the null pointer reference vulnerability.Use the MD5 check to check the file.

Log: Fix the null pointer reference vulnerability.
Bug: https://pms.uniontech.com/bug-view-252519.html

src/service/filehander.cpp

@@ -823,7 +823,7 @@ bool FileHander::isDdfFileDirty(const QString &filePath)const
                 if (md5 != nMd5) {
                     return true;
                 }
-            } else  if (ver == EDdfUnknowed) {
+            } else{
                 return true;
             }
             return false;