#44 dataxvalue does not work with variables any more

[Uli]

Using GLE 4.2.5 on Ubuntu 16/04:
Expressions like the following
! having read a data set d1 from file containing 20 lines
let d2=dataxvalue(d1,x), datayvalue(d1,x) from 1 to 5
result in the following error:

Error: index out of range: 0 (1 ... 20)