id,summary,reporter,owner,description,type,status,priority,milestone,component,resolution,keywords,cc,planetversion,pltversion
208,(string->number x 10) expects string but is getting #<sql-null>,gknauth,jaz,"string->number: expects type <string> as 1st argument, given: #<sql-null>; other arguments were: 10

I get this error with the following:

(query-rows (string-append
             ""select a.type, ""
             ""a.number, ""
             ""a.due, ""
             ""w.submitted, ""
             ""w.raw_grade, ""
             ""w.adj_grade, ""
             ;""w.extension, ""
             ""a.description ""
             ""from work w ""
             ""join assignment as a on w.fk_assignment=a.id ""
             ""join term as te on te.code='F09' and a.fk_term=te.id ""
             ""join student as s on s.handle='student123' ""
             ""join course as co on co.code='CPTR 346' ""
             ""join class as cl on cl.fk_course=co.id and cl.fk_term=te.id ""
             ""join enrollee as e on w.fk_enrollee=e.id and e.fk_student=s.id and e.fk_class=cl.id ""
             ""order by a.type, a.number""))

I can proceed without the error if I comment out the line:
             ""w.adj_grade, ""

MySQL type of w.adj_grade is float.

I've traced the error to line 1911 of mysql.plt v1.5, inside text-decoder-map.

Apparently x is supposed to be a string, but sometimes it's #<sql-null>.
",defect,closed,major,,jaz/mysql.plt,fixed,,,(1 5),4.2.1.8