Image game: filter out deleted/non-existent files

[Waldir Pimenta]

Example: Q16939937's ptwiki article includes the non-existent image Cleofe.jpg, which the game tries to load, showing the string "Loading..." indefinitely.

[Hsarrazin]

and also images that are not on commons, but on the local wp (or put them on a list to check for import on commons).

ex. on Item Q5219684 - the pic is on enwiki