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Black Box: correct order of validation checks for "F" commands

It doesn't do much good to range-check an argument after using it as
an array index.

--- a/blackbox.c

+++ b/blackbox.c

@@ -1067,9 +1067,9 @@

     case 'F':

         sscanf(move+1, "%d", &rangeno);

-        if (ret->exits[rangeno] != LASER_EMPTY)

-            goto badmove;

         if (!RANGECHECK(ret, rangeno))

+            goto badmove;

+        if (ret->exits[rangeno] != LASER_EMPTY)

             goto badmove;

         fire_laser(ret, rangeno);

         break;