[1.5.4] Upgrade gestures.

Author: IIzzaya

Runtime/gestures/multitap.cs

@@ -316,7 +316,9 @@ public MultiTapGestureRecognizer(
             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;