Hi Bastien,

Sorry about the formatting -- that's annoying.  I've attached the patch. 
  Here's its description:

Currently there isn't an easy way to have default cell values which 
differ from one propview block to another.  This patch enables one to 
specify what a cell's default value for a block should be.  For example, 
with this patch applied, you can do something like:

     #+BEGIN: propview :id " mytable" :defaultval "" :cols (PROP1 PROP2)

in order to make the default value for this block to be "" instead of 0 
in the case that PROP1 or PROP2 isn't contained as a property of a headline.

Regards,

Mark