[1.5.4] Upgrade gestures.

Runtime/gestures/multitap.cs

             TimeSpan? longTapDelay = null,
             object debugOwner = null,
             PointerDeviceKind? kind = null
-        ) : base(debugOwner: debugOwner, kind: kind) { }
+        ) : base(debugOwner: debugOwner, kind: kind) {
+            this.longTapDelay = longTapDelay ?? TimeSpan.Zero;
+        }
 
         GestureMultiTapDownCallback onTapDown;