Update odf.php

I don't know why but this difference betwenn the old versionand the new one in Dolibarr make crash "Error during file export addFromString" the doc_generic_project_odt.modules.php. I compare the new version and the older and this is the only thing I found. If I remove this require_one it works fine.

EDIT :
I understand, in line 73 it : include_once('zip/'.$zipHandler.'.php');
But as you require_one them before, PHP include it twice and break the rule, lost the pointer and so on...
Tell me if I'm right (I've got a problem like that before, the _once seem to protect me agains taht, but somtimes it do a mess)