When trying out

     function{
         pigment {
             image_map{
                 tga "bad.tga" 
             }	  

with SuperPatch, I found that if the image_map file doesn't exist
or can't be read (etc), and POV tries to do its Error exit routine, 
it was crashing instead. 
The reason seems to be that in Pattern_Structure, 
the image is a member of a C union ('Vals') which I think 
is being initialized to a value for 'gradient',
so when POV tries to free up the Pattern_Structure in 
order to quit, it sees the image pointer as not NULL
and tries to free the image and causes SIGSEGV. 

a fix is very simple in parstxtr.c:

static void Parse_Pattern (TPATTERN *New, int TPat_Type)
{
[ ... ]

     CASE (IMAGE_MAP_TOKEN)
       if (TPat_Type != PIGMENT_TYPE)
       {
	 Only_In("image_map","pigment");
       }

       if (Old_Type==BITMAP_PATTERN) 
       {
	 Destroy_Image(Old_Image);
       }   

       New->Type = BITMAP_PATTERN;
       New->Frequency = 0.0;

       /*a "fix"*/
       New->Vals.Image=NULL;
       /*---*/

       Parse_Image_Map ((PIGMENT *)New);
       EXIT
     END_CASE
[ ... ]

Density_File is part of the same union and may have a similar
problem. but I haven't even tried to find out.

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