Should this not be an error ?

[Alex Tweedly]

I have a line of script that *should* have read
    if the last line of t is empty then delete line -1 of t
but I mis-typed it, and instead of the '1' key, I hit the adjacent key, 
and got a back quote (`), so I had
    if the last line of t is empty then delete line -` of t


This script compiled OK, but obviously did the wrong thing (I'm not sure 
what it did - I can't find the back-quote in the dctionary).

Shouldn't this be a compile error ?
Or is it a missing dictionary entry, and the line has some real but 
obscure interpretation ?

-- Alex.