Removing spaces before command

Question

When using French guillemets with TeX4HT, the resulting symbols are not followed/preceded by non-breaking spaces like they should, resulting in wrong line-breaking in HTML.

I tried resetting \og and \fg with a babel.4ht file, but I can't get anything working. The only solution I've found so far is the following:

I defined new \Og and \Fg commands with:

\ifluatex
  \newcommand{\Og}{\og}
  \newcommand{\Fg}{\fg{}}
\else
  \newcommand{\Og}{\HCode{« }}
  \newcommand{\Fg}{\HCode{ »}}
\fi

together with a sed hack to remove the spaces before  :

sed -i "s@ *  *@\ @g" $HTML

I'd like to get rid of this and do it properly in a .4ht file. How could I do this?

Edit:

The \Og/\Fg hack is actually acceptable for me, but not the sed one, so I'm modifying the title of this question: How can I remove spaces before the command?