2.4.6 to 3.1.2 Upgrade fails on PKPSubmissionFileDAO.inc.php

I’m having trouble upgrading from version 2.4.6 to 3.1.2
The upgrade does not finish and shows the following errors below:

[code: Installer Installer::setFileUploader]

[code: Installer Installer::setFileName]
PHP Warning: get_class() expects parameter 1 to be object, null given in /public/lib/pkp/classes/submission/PKPSubmissionFileDAO.inc.php on line 358
PHP Fatal error: Uncaught Error: Call to a member function getFilePath() on null in/public/lib/pkp/classes/submission/PKPSubmissionFileDAO.inc.php:377
Stack trace:
0 public/classes/install/Upgrade.inc.php(991): PKPSubmissionFileDAO->updateObject(Object(SubmissionFile))
1 /public/lib/pkp/classes/install/Installer.inc.php(415): Upgrade->setFileName(Object(Upgrade), Array)
2 /public/lib/pkp/classes/install/Installer.inc.php(265): Installer->executeAction(Array)
3 /public/lib/pkp/classes/install/Installer.inc.php(186): Installer->executeInstaller()
4 /public/lib/pkp/classes/cliTool/UpgradeTool.inc.php(88): Installer->execute()
5 /public/lib/pkp/classes/cliTool/UpgradeTool.inc.php(64): UpgradeTool->upgrade()
6 /public/tools/upgrade.php(34): UpgradeTool->execute()
7 {main}
thrown in /public/lib/pkp/classes/submission/PKPSubmissionFileDAO.inc.php on line 377
:~/public/tools$

Thanks in advance
Sandro