if (rune_array[ you.inv[d].plus ] == 0)

                num_runes += you.inv[d].quantity;
                // Don't assert in rune_array[] due to buggy runes,
                // since checks for buggy runes are already done
                // elsewhere.
                if (you.inv[d].plus < 0 || you.inv[d].plus >= NUM_RUNE_TYPES)
                {
                    mpr("WARNING: Buggy rune in pack!");
                    // Be nice and assume the buggy rune was originally
                    // different from any of the other rune types.

                    continue;
                }

                num_runes += you.inv[d].quantity;

                if (rune_array[ you.inv[d].plus ] == 0)
                    num_diff_runes++;