msCopyMap causes segfault in absence of fontset

[sgillies@…]

For a mapObj created from a map file with no fontset definition, the msCopyMap
function used in mapObj::clone() segfaults.

A work around may be to declare an empty fontset file.  This works for me, 
but I only tested with a MapServer with truetype support enabled.  Will 
check to see if the bug can be avoided when there is no truetype support.

The fix shouldn't be too much, just check to see if there is a fontset 
beforing calling the msCopyFontSet function.

[sgillies@…]

Patch to mapcopy.c fixing bug 470

[sgillies@…]

This bug is fixed in main CVS and branch-4-0.  A patch is also attached and 
should be applied to the 4.0.1 mapserver release.  Two lines in mapcopy.c
are replaced by one line.

If for some reason a user cannot or does not want to patch and recompile, the
bug can be avoided by executing one extra statement in the mapscript application.
Before calling the clone() method of a mapObj with no defined fontset, simply
set the mapObj's fontset.filename to something other than a NULL value.  
For example:

    mapobj = mapObj('nofontset.map')
    mapobj.fontset.filename = ''
    clone_mapobj = mapobj.clone()

If the map file defines a fontset, mapobj.fontset.filename begins with a
non-NULL value and the bug will not occur, so do not bind a new value to 
the fontset.filename.