Bar chart overcounts?

[benknoble]

graphite/graphite-lib/bar.rkt

Line 68 in 6155173

(hash-update! count-tbl ((gr-x-conv) x) add1 1))

I think this line of code makes the hash-table overcount, reporting 10 observations if there were only 9, for example, since add1 is applied to the default 1 when inserting the first value. Changing to 0 should be correct.