Ok I see.
using "python:item.title or default" or even cleaner, a tales-statement: "item/title | default" just might help.. I also think that the later is cleaner, but it doesn't work for me. I did: <td tal:content="item/title | default">No Title</td>
But I got the same results when doing: <td tal:content="item/title">No Title</td>
Correct me if I'm wrong, but after thinking about it, I deducted that the "or" in a tales-statement: <td tal:content="item/title | default">No Title</td> doesn't work like the "or" of python: <td tal:content="python: item.title or default"> because for python the empty string is false while the tales-statement returns true if the variable exist without caring about its value. I think this should be fixed because the second solution adds unnecesary complexity to the tal-expression and I also think that it's an inconsistency that one works and the other don't.