OCCURS DEPENDING ON variables not handled correctly

We have a wonderful comment in AddEmUp:

    # Processing of arrays can involve 123*b_37 + 456 (offset) or 30*b_454 (length),
    # and I've been warned that there might even be parentheses involved.
    # We'll burn those bridges in times to come.

Currently those are completely skipped, which seems very suspicious. Either the resulting fields are not necessary - then they should be removed - or they just knowingly use wrong values.

Please fix the later - either by resolving the values as noted in the comments, or by returning a None instead + check this on use to not work with the variable's unknown length and offset (which may means that they can't be handled at all for now).