Setting background image to NULL in SY_File will cause an error on login : "Object reference not set to an instance of an object"Object reference not set to an instance of an object"

Setting background image to NULL in SY_File will cause an error on login : "Object reference not set to an instance of an object"Object reference not set to an instance of an object".

Steps to reproduce:

• Open System configuration form, System tab - check "UseBackgroundPicture" setting.
• Save and logout
• Run the following script to set the image to NULL :

  UPDATE SY_File SET FileBinary = NULL WHERE FileID = (SELECT TOP 1 Contents FROM SY_SysValues WHERE IDKey = 'BackgroundPicture' AND Section = 'System')
  

The error will then occur on login.

Note that scripts often used to remove all attachments / documents from databases will cause this issue also.