Fix vision when door is destroyed by ray effect

A door was destroyed and vision unblocked without considering
temporary (poison) clouds.

src/zap.c

@@ -5404,7 +5404,7 @@ zap_over_floor(
                     add_damage(x, y, 0L);
             }
             lev->doormask = new_doormask;
-            unblock_point(x, y); /* vision */
+            recalc_block_point(x, y); /* vision */
             if (see_it) {
                 pline1(see_txt);
                 newsym(x, y);