Prefer LINE_EXISTS to READ TABLE or LOOP AT

[lucasborin]

If it finds a READ TABLE or LOOP with TRANSPORTING NO FIELDS or without ASSIGNING or INTO = Raise error.

https://github.com/SAP/styleguides/blob/master/clean-abap/CleanABAP.md#prefer-line_exists-to-read-table-or-loop-at