bugfix: undo drawing creation

Dependencies

• [2] 73OCE2MC after much struggle, a brute-force undo
• [3] 6DE7RBZ6 move mouse_released events to Drawing
• [4] WTDKUACN rectangle and square shapes
• [5] VHQCNMAR several more modules
• [*] OTIBCAUJ love2d scaffold
• [*] DLQMM265 scroll past first page
• [*] BLWAYPKV extract a module

Change contents

• edit in main.lua at line 145
  [8.890]

  [8.890]
  + Drawing.before = snapshot_everything()
• replacement in drawing.lua at line 351
  [3.3159]→[2.8285:8359](∅→∅)
  − record_undo_event({before=Drawing.before, after=snapshot_everything()})
  [3.3159]

  [3.19072]
  + if Drawing.before then

  + record_undo_event({before=Drawing.before, after=snapshot_everything()})

  + Drawing.before = nil

  + end