Bug 1883: Directory reading cannot be cancelled for SFTP servers that provide optional end-of-list field

https://winscp.net/tracker/1883
(cherry picked from commit 34785ac865b7e9148167a5be95c92baefb485934)

Source commit: 011e018b801342438b817242b69bdbae947914cc

source/core/SftpFileSystem.cpp

@@ -3472,7 +3472,8 @@ void __fastcall TSFTPFileSystem::ReadDirectory(TRemoteFileList * FileList)
           }
         }
 
-        if ((FVersion >= 6) &&
+        if (!isEOF &&
+            (FVersion >= 6) &&
             // As of 7.0.9 the Cerberus SFTP server always sets the end-of-list to true.
             // Fixed in 7.0.10.
             (FSecureShell->SshImplementation != sshiCerberus) &&