[5.0] Error when export an empty field

Hi

When i try to export (gtk client), with an empty field, i have this traceback

I have made patch to correct this issue, see below

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[2009-09-07 00:07:14,777] ERROR:web-services01]:
[2009-09-07 00:07:14,778] ERROR:web-services02]: Environment Information :
[2009-09-07 00:07:14,778] ERROR:web-services03]: System : Linux-2.6.28-15-generic-x86_64-with-Ubuntu-9.04-jaunty
[2009-09-07 00:07:14,778] ERROR:web-services04]: OS Name : posix
[2009-09-07 00:07:14,779] ERROR:web-services05]: Distributor ID: Ubuntu
[2009-09-07 00:07:14,779] ERROR:web-services06]: Description: Ubuntu 9.04
[2009-09-07 00:07:14,779] ERROR:web-services07]: Release: 9.04
[2009-09-07 00:07:14,779] ERROR:web-services08]: Codename: jaunty
[2009-09-07 00:07:14,779] ERROR:web-services09]: Operating System Release : 2.6.28-15-generic
[2009-09-07 00:07:14,779] ERROR:web-services10]: Operating System Version : #49-Ubuntu SMP Tue Aug 18 19:25:34 UTC 2009
[2009-09-07 00:07:14,780] ERROR:web-services11]: Operating System Architecture : 64bit
[2009-09-07 00:07:14,780] ERROR:web-services12]: Operating System Locale : fr_FR.UTF8
[2009-09-07 00:07:14,780] ERROR:web-services13]: Python Version : 2.6.2
[2009-09-07 00:07:14,780] ERROR:web-services14]: OpenERP-Server Version : 5.0.5-bzr
[2009-09-07 00:07:14,780] ERROR:web-services15]: Last revision No. & ID : 1856 <email address hidden>
[2009-09-07 00:07:14,780] ERROR:web-services16]: Traceback (most recent call last):
[2009-09-07 00:07:14,780] ERROR:web-services17]: File "/home/alnslang/bzrsyleam/openerp/5.0/officiel/server/bin/osv/osv.py", line 59, in wrapper
[2009-09-07 00:07:14,781] ERROR:web-services18]: return f(self, dbname, *args, **kwargs)
[2009-09-07 00:07:14,781] ERROR:web-services19]: File "/home/alnslang/bzrsyleam/openerp/5.0/officiel/server/bin/osv/osv.py", line 118, in execute
[2009-09-07 00:07:14,781] ERROR:web-services20]: res = pool.execute_cr(cr, uid, obj, method, *args, **kw)
[2009-09-07 00:07:14,782] ERROR:web-services21]: File "/home/alnslang/bzrsyleam/openerp/5.0/officiel/server/bin/osv/osv.py", line 110, in execute_cr
[2009-09-07 00:07:14,782] ERROR:web-services22]: return getattr(object, method)(cr, uid, *args, **kw)
[2009-09-07 00:07:14,782] ERROR:web-services23]: File "/home/alnslang/bzrsyleam/openerp/5.0/officiel/server/bin/osv/orm.py", line 541, in export_data
[2009-09-07 00:07:14,782] ERROR:web-services24]: datas += self.__export_row(cr, uid, row, fields_to_export, context)
[2009-09-07 00:07:14,782] ERROR:web-services25]: File "/home/alnslang/bzrsyleam/openerp/5.0/officiel/server/bin/osv/orm.py", line 500, in __export_row
[2009-09-07 00:07:14,782] ERROR:web-services26]: dt+=rr.name+','
[2009-09-07 00:07:14,783] ERROR:web-services27]: TypeError: unsupported operand type(s) for +: 'bool' and 'str'
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