cursor duplication

[felixroos]

spotted by @Bhatck-Aegol : when clicking outside the document (like console) then into another box (where the cursor is not),
then 2 cursors will be visible, until the cursor is moved again

[felixroos]

this also happens in flok.cc

[TodePond]

could maybe clear cursors somehow when this event fires
https://developer.mozilla.org/en-US/docs/Web/API/Document/visibilitychange_event

[felixroos]

some more findings by @Bhatck-Aegol

"
causes cursor duplication bug:

• Click out of the window then into another box
• Go into settings or about then click another box
• Enter Zen mode then click another box
• Go to another box via TAB
• Click select language thing then into another box
  sometimes doesn't happen???
  trying to dupe from the top right box doesn't work??
  dupind from other windows work fine
  much weird
  duplicated cursor only disappears when:
• Code is being highlited in the duped cursor's box, like in a playing strudel box
• Another cursor moves in the box (not sure, more research needed)
• basically when box is updated
  hypothesis:
  Cursor code doesn't properly detect when it's no longer active and isn't hidden.
  When a box updates it clears all inactive cursors.
  Cursor doesn't update box properly and as such doesn't get cleared.
  (Now the work is up to the devs :D)
  "