About "d" attribute

Hi,
Just notice this:
8.3.9 The grammar for path data
Note that the BNF allows the path ‘d’ attribute to be empty. This is
not an error, instead it disables rendering of the path.

Real strange!
Reason:
if d is empty, there is  no path at all. so no render, so disable
what?  Bad logic?
Who will write empty path node? Some one eat enough, nothint to do?

Regards
Qinxian