fix dynamic images for osx

dashboard-ui/scripts/itemlistpage.js

@@ -60,6 +60,7 @@
 
                 itemsContainer.classList.remove('vertical-list');
                 itemsContainer.classList.add('vertical-wrap');
+                itemsContainer.classList.add('centered');
             }
             itemsContainer.innerHTML = '';
         }

dashboard-ui/strings/en-US.json

@@ -2300,7 +2300,7 @@
   "LabelffmpegVersion": "FFmpeg version:",
   "LabelffmpegPathHelp": "The path to your downloaded FFmpeg application, or folder containing FFmpeg.",
   "SetupFFmpeg": "Setup FFmpeg",
-  "SetupFFmpegHelp": "FFmpeg is a required component and needs to be configured.",
+  "SetupFFmpegHelp": "Emby may require a library or application to convert certain media types. There are many different applications available, however, Emby has been tested to work with ffmpeg. Emby is in no way affiliated with ffmpeg, its ownership, code or distribution.",
   "EnterFFmpegLocation": "Enter FFmpeg path",
   "DownloadFFmpeg": "Download FFmpeg",
   "FFmpegSuggestedDownload": "Suggested download: {0}",