Fixed max width of filter buttons.

inabox.wpf/Forms/FilterButton.cs

@@ -85,7 +85,7 @@ public class FilterButton<T> : Button
 
         if (!string.IsNullOrEmpty(text))
         {
-            MaxWidth = double.MaxValue;
+            stackPnl.MaxWidth = double.MaxValue;
             var lbl = new Label();
             lbl.Content = text;
             lbl.VerticalAlignment = VerticalAlignment.Stretch;
@@ -96,7 +96,7 @@ public class FilterButton<T> : Button
         }
         else
         {
-            MaxWidth = 30;
+            stackPnl.MaxWidth = 30;
         }
 
         Content = stackPnl;