I am updating from Exchange 2010 sp1 to Exchange 2010 sp 3 and I get an error

Error:

The following error was generated when "$error.Clear();

         if ($RoleCreatePublicFolderDatabase)

         {

           $publicDB = get-PublicFolderDatabase -Server:$RoleFqdnOrName -ErrorAction SilentlyContinue;

           $DB = get-MailboxDatabase -Server:$RoleFqdnOrName -ErrorAction SilentlyContinue;

           if ($publicDB -and $DB)

           {

               set-mailboxdatabase `

                 -Identity:$DB.Identity `

                 -publicFolderDatabase:$publicDB.Identity `

                 -DomainController $RoleDomainController

            }                 

          }

        " was run: "Cannot bind argument to parameter 'Identity' because it is null.".

The following error was generated when "$error.Clear(); if ($RoleCreatePublicFolderDatabase) { $publicDB = get-PublicFolderDatabase -Server:$RoleFqdnOrName -ErrorAction SilentlyContinue; $DB = get-MailboxDatabase -Server:$RoleFqdnOrName -ErrorAction SilentlyContinue; if ($publicDB -and $DB) { set-mailboxdatabase -Identity:$DB.Identity -publicFolderDatabase:$publicDB.Identity -DomainController $RoleDomainController } }" was run:"Cannot bind argument to parameter 'Identity' because it is null