add an assert

Dependencies

• [2] KKMFQDR4 editing source code from within the app
• [*] BULPIBEG beginnings of a module for the text editor
• [*] Z5HLXU4P add state arg to a few functions
• [*] MXA3RZYK deduce left/right from state where possible

Change contents

• edit in text.lua at line 430
  [5.6132]

  [6.1281]
  + assert(State.cursor1.pos)
• edit in source_text.lua at line 489
  [2.114995]

  [2.114995]
  + assert(State.cursor1.pos)