Update UserProfileOverlay and ClickableAvatar to treat system users more correctly

osu.Game/Overlays/UserProfileOverlay.cs

@@ -41,7 +41,7 @@ namespace osu.Game.Overlays
 
         public void ShowUser(IUser user)
         {
-            if (user == APIUser.SYSTEM_USER)
+            if (user.OnlineID == APIUser.SYSTEM_USER_ID)
                 return;
 
             Show();

osu.Game/Users/Drawables/ClickableAvatar.cs

@@ -21,7 +21,7 @@ namespace osu.Game.Users.Drawables
         /// </summary>
         public bool OpenOnClick
         {
-            set => clickableArea.Enabled.Value = value;
+            set => clickableArea.Enabled.Value = clickableArea.Action != null && value;
         }
 
         /// <summary>
@@ -52,8 +52,10 @@ namespace osu.Game.Users.Drawables
             Add(clickableArea = new ClickableArea
             {
                 RelativeSizeAxes = Axes.Both,
-                Action = openProfile
             });
+
+            if (user?.Id != APIUser.SYSTEM_USER_ID)
+                clickableArea.Action = openProfile;
         }
 
         [BackgroundDependencyLoader]