[web] fix muledit rendering bug
form.cw_col might be None and explicitly passing None to the selector
chain may crash. Most __call__ methods of selectors are defined as in :
def __call__(self, cls, req, rset, row=None, col=0, **kwargs)
and then manipulate col as if it's an integer.
debian/tmp/usr/lib/PY_VERSION/site-packages/cubicweb/web usr/lib/PY_VERSION/site-packages/cubicweb
debian/tmp/usr/share/cubicweb/cubes/shared/data usr/share/cubicweb/cubes/shared
debian/tmp/usr/share/cubicweb/cubes/shared/wdoc usr/share/cubicweb/cubes/shared