Fix doc: \encode needs a space before it

[[Imported from SVN: r8358]]

dune/fufem/functions/portablepixelmap.hh

@@ -247,7 +247,7 @@ class ColorMap
          *   \f]
          *   (for notation \f$\tau, \gamma\f$ see above)
          *   \warning In order to be of any real use <var>color</var> is not restricted to values in the filled in ColorKey. This, however, leads to possibly highly inaccurate if not meaningless results, if <var>color</var>
-         *   is too "far away" of the colors in the ColorKey. Also \code x==inv_map(fMin,fMax,map(fMin,fMax,x))\endcode will probably evaluate as <tt>false</tt>. So inv_map() is ONLY a hopefully APPROXIMATE inverse of map().
+         *   is too "far away" of the colors in the ColorKey. Also \code x==inv_map(fMin,fMax,map(fMin,fMax,x)) \endcode will probably evaluate as <tt>false</tt>. So inv_map() is ONLY a hopefully APPROXIMATE inverse of map().
          *
          *   \param fMin lower interval boundary for values represented by the colormap
          *   \param fMax upper interval boundary for values represented by the colormap