when naming points, allow backspacing back to ''

Dependencies

• [2] MP2TBKU6 bugfix: crash in Text.up() after return
• [*] OTIBCAUJ love2d scaffold
• [*] BYG5CEMV support for naming points

Change contents

• edit in main.lua at line 555
  [2.1655]

  [5.837]
  + if len == 1 then byte_offset = 0 end