fixed a crash which happened if there were no pads at all.

pcbnew/export_gencad.cpp

@@ -183,7 +183,10 @@ void CreatePadsShapesSection( FILE* file, BOARD* pcb )
  *  pour les formes de pad PAD1 a PADn
  */
 {
-    D_PAD* pad, ** padlist, ** pad_list_base;
+    D_PAD*      pad;
+    D_PAD**     padlist;
+    D_PAD**     pad_list_base = NULL;
+    
     const  char*  pad_type;
     int    memsize, ii, dx, dy;
     D_PAD* old_pad = NULL;
@@ -191,11 +194,14 @@ void CreatePadsShapesSection( FILE* file, BOARD* pcb )
 
     fputs( "$PADS\n", file );
 
+    if( pcb->m_NbPads > 0 )
+    {
         // Generation de la liste des pads tries par forme et dimensions:
         memsize = (pcb->m_NbPads + 1) * sizeof(D_PAD *);
         pad_list_base = (D_PAD**) MyZMalloc( memsize );
         memcpy( pad_list_base, pcb->m_Pads, memsize );
         qsort( pad_list_base, pcb->m_NbPads, sizeof(D_PAD *), Pad_list_Sort_by_Shapes );
+    }
 
     pad_name_number = 0;
     for( padlist = pad_list_base, ii = 0; ii < pcb->m_NbPads; padlist++, ii++ )
@@ -295,6 +301,8 @@ void CreatePadsShapesSection( FILE* file, BOARD* pcb )
     }
 
     fputs( "$ENDPADS\n\n", file );
+    
+    if( pad_list_base )
         MyFree( pad_list_base );
 }