scroll bug fix (fix sign)

Runtime/ui/geometry.cs

         }
 
         public static int sign(this float value) {
-            return (int) Mathf.Sign(value);
+            return value == 0.0f ? 0 : value > 0.0f ? 1 : -1;
         }
 
         public static bool isInfinite(this float it) {
             if (other == null || other.isEmpty) {
                 return this;
             }
-            
+
             return fromLTRB(
                 Mathf.Min(this.left, other.left),
                 Mathf.Min(this.top, other.top),

Runtime/widgets/scroll_activity.cs

 
             this._lastDetails = details;
 
-            if (this._retainMomentum && velocity != 0.0f && velocity.sign() == this.carriedVelocity.Value.sign()) {
+            if (this._retainMomentum && velocity.sign() == this.carriedVelocity.Value.sign()) {
                 velocity += this.carriedVelocity.Value;
             }