Move Character Portrait nulls to end of list

Assets/Fungus/Scripts/Components/Character.cs

@@ -184,7 +184,10 @@ namespace Fungus
 
         protected virtual void OnValidate()
         {
-            portraits.Sort(PortraitUtil.PortraitCompareTo);
+            if (portraits != null && portraits.Count > 1)
+            {
+                portraits.Sort(PortraitUtil.PortraitCompareTo);
+            }
         }
     }
 }

Assets/Fungus/Scripts/Utils/PortraitUtils.cs

@@ -189,9 +189,9 @@ namespace Fungus
             if (x == y)
                 return 0;
             if (y == null)
-                return 1;
-            if (x == null)
                 return -1;
+            if (x == null)
+                return 1;
 
             return x.name.CompareTo(y.name);
         }