question on user-error reference leading out of table

[Mario Frasca]

Hi,

I need some help understanding how to use org-mode/org-table for 
references leading outside my table.

I have a series of daily figures, and I am computing the series of 
running sums.  column one is the daily data, column two is the running 
sum of the preceding 14 values from column 1.

http://ix.io/2qu7

problem is the @-13$1 reference in the function for the second column: 
it hits a software-generated "user-error: Row descriptor -13 leads 
outside table".

this happens even if the formula says (if (> @# 13) (apply '+ 
'(@-13$1..$1)) 0), that is, even if the formula is not evaluated on the 
cells where the reference does indeed lead out of the table.

this happens around line 2809 of org-table.el, inside org-table--row-type

I've tried to catch the user-error with a `condition-case', but even 
there, the error seems to happen before evaluation.

I've replaced the `(user-error)' function with a `nil', and it works for 
me, but that's a very rough measure I'm afraid.