Use a placeholder icon when an icon is unable to load/be found in the plugin directory

[NekoJonez]

Like shown in the screenshot, sometimes when going through the plugin directory in your WP install... for some reason a plugin icon is unable to load since there isn't one/it's missing/it's too big/blocked by AV/... In that case, it would be nice that some placeholder art is shown like the WP logo or the one in "second screen".

[nikunj8866]

@audrasjb I don't think this needs a Core patch.

Plugin icons in wp-admin are pulled from plugins_api, where the recommended size is 256×256 px, and smaller variants (128×128, 64×64) are generated automatically. SVG is also supported. (Ref: Plugin Icons documentation​https://make.wordpress.org/plugins/2014/08/21/plugin-icons/). These aren't "too big" and Core already handles appropriate sizing.

The only time a broken image is seen in wp-admin is when the request fails due to a local network issue (e.g. connectivity problems, firewall, ad-blocker, antivirus). In those cases, Core can't fix the root problem by replacing the broken image with a local placeholder would only mask a temporary connectivity issue.