Oops, choose the *first* PNG from the manifest, to avoid reference art

When we moved more logic into the main app, we made some assumptions
about manifest art that were different than Impress 2020's, in hopes
that they would be More Correct for potential future edge cases.

Turns out, they were actually *less* correct for *current* edge cases!
Chips linked us to a few examples, including this Reddit post:

https://www.reddit.com/r/neopets/comments/1b8fd72/i_dont_think_thats_the_correct_image/

Fixed now!

app/models/swf_asset.rb

@@ -131,13 +131,13 @@ class SwfAsset < ApplicationRecord
         # seen!
         { js: assets_by_ext[:js].last }
       else
-        # Otherwise, return the last PNG and the last SVG, arbitrarily.
-        # (There's probably only one of each! I'm just going by the same logic
-        # we've seen in the JS library case, that later entries are more likely
-        # to be correct.)
+        # Otherwise, return the first PNG and the first SVG. (Unlike the JS
+        # case, it's important to choose the *first* PNG, because sometimes
+        # reference art is included in the manifest, like with the Stealthy
+        # Eyrie Shirt's asset 304486_b28cae0d76.)
         {
-          png: assets_by_ext.fetch(:png, []).last,
-          svg: assets_by_ext.fetch(:svg, []).last,
+          png: assets_by_ext.fetch(:png, []).first,
+          svg: assets_by_ext.fetch(:svg, []).first,
         }
       end
     rescue StandardError => error