gracefully handle a non-existent filename at the commandline

Dependencies

• [2] 5T2E3PDV couple of bugfixes to file-handling
• [3] YKRF5V3Z starting to load/save
• [4] Z4KNS42N to open a file without a terminal, drag it on!
• [5] 2C7CTIQY make space for multiple kinds of width
• [6] HDC3AAQP silly reason my screenshots had an ugly black line down the left
• [7] NZ7V4BVS note card
• [8] OTIBCAUJ love2d scaffold
• [9] QU7NHFOV show cursor
• [10] XX7G2FFJ intermingle freehand line drawings with text
• [11] 4NDYV4WD fix 2 bugs in line selection

Change contents

• replacement in main.lua at line 81
  [3.336]→[3.2:15](∅→∅)
  − local text
  [3.336]

  [3.44]
  + local text = love.graphics.newText(love.graphics.getFont(), '')
• replacement in main.lua at line 817
  [2.57]→[3.206:223](∅→∅),[3.206]→[3.206:223](∅→∅)
  − infile:close()
  [2.57]

  [3.223]
  + if infile then infile:close() end
• edit in main.lua at line 835
  [3.613]

  [3.613]
  + if #result == 0 then

  + table.insert(result, '')

  + end