fix memory leak

backend/lexmark_x2600.c

@@ -625,10 +625,17 @@ attach_one (SANE_String_Const devname)
 
 SANE_Status
 scan_devices(){
+  DBG (2, "scan_devices\n");  
   SANE_Char config_line[PATH_MAX];
   FILE *fp;
   const char *lp;
   num_devices = 0;
+
+  if(first_device){
+    DBG (2, "    free first_device\n");
+    free(first_device);
+  }
+  
   first_device = NULL;
 
   fp = sanei_config_open (LEXMARK_X2600_CONFIG_FILE);