bug 314042 sane-hp4200.patch

- apply patch from Nickolai Zeldovich (nickolai-guest) to fix a
  potential division by 0

backend/hp4200.c

@@ -929,10 +929,13 @@ compute_dpd (HP4200_Scanner * s, int step_size, int line_end)
 		  s->hw_parms.pulse_duration + 1) +
 		 3 - s->hw_parms.num_tr_pulses));
 
+  if (tr == 0)
+    return 0;
+
   dpd = (((s->hw_parms.fsteps_25_speed * 4) +
 	  (s->hw_parms.fsteps_50_speed * 2) +
 	  s->hw_parms.steps_to_reverse) * 4 * step_size) % tr;
-  dpd = (tr == 0) ? 0 : tr - dpd;
+  dpd = tr - dpd;
 
   return dpd;
 }