Return poster placeholder url when trakt doesn't have one

NzbDrone.Core/MetadataSource/TraktProxy.cs

@@ -82,6 +82,8 @@ namespace NzbDrone.Core.MetadataSource
 
         private static string GetPosterThumbnailUrl(string posterUrl)
         {
+            if(posterUrl.Contains("poster-small.jpg")) return posterUrl;
+
             var extension = Path.GetExtension(posterUrl);
             var withoutExtension = posterUrl.Substring(0, posterUrl.Length - extension.Length);
             return withoutExtension + "-138" + extension;

UI/AddSeries/addSeries.css

@@ -65,3 +65,8 @@
     padding-left: 20px;
     padding-top: 10px;
 }
+
+.img-polaroid {
+    min-width: 138px;
+    min-height: 203px;
+}