FMSLogo Code

The problem was that parenthesizing/treeifying the expression
failed, since 1 is not a procedure and therefore FMSLogo doesn't
know how many parameters it should take. The "tree" of 1 was
then dereferenced to get the "car" field, which crashed.

The fix, which copied from UCBLogo, is to use the tree as-is
if it's not a list (that is, don't dereference it). This results
in a "i don't know what how to 1" error, which I think is the
correct error for such an expression.