Until OC 9.1 there was a workaround for SVG icons for IE8/9 that
required having a PNG version of the icons.
Since we don't support IE < 11 any more in OC 9+, the workaround was
removed on master/9.2: https://github.com/owncloud/core/pull/25240
Please note that the PNG icons were also removed, so if any of your apps
were using the PNG icons from core instead of the SVG ones, please make
sure they do use the SVG ones from now on. (they should have in the