From bc47dedf27d5119243da88c340aebd7231973c74 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Sun, 28 May 2017 21:34:15 +0900
Subject: [PATCH] Add non-null assertion

---
 osu.Game/Overlays/ChatOverlay.cs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/osu.Game/Overlays/ChatOverlay.cs b/osu.Game/Overlays/ChatOverlay.cs
index fec5f11129..d442fe5db0 100644
--- a/osu.Game/Overlays/ChatOverlay.cs
+++ b/osu.Game/Overlays/ChatOverlay.cs
@@ -148,6 +148,8 @@ namespace osu.Game.Overlays
 
         protected override bool OnDrag(InputState state)
         {
+            Trace.Assert(state.Mouse.PositionMouseDown != null);
+
             chatHeight.Value = startDragChatHeight - (state.Mouse.Position.Y - state.Mouse.PositionMouseDown.Value.Y) / Parent.DrawSize.Y;
             return base.OnDrag(state);
         }