wip2

Author: ikpil

src/Box2D.NET/B2World.cs

@@ -242,7 +242,7 @@ public void Clear()
             userTaskContext = null;
             userTreeTask = null;
 
-            userData = new B2UserData();
+            userData = B2UserData.Empty;
 
             inv_h = 0.0f;
             inv_dt = 0.0f;

test/Box2D.NET.Test/B2WorldTest.cs

@@ -321,7 +321,7 @@ public void TestWorldCoverage()
 
         b2World_SetUserData(worldId, B2UserData.Double(value));
         var userData = b2World_GetUserData(worldId);
-        Assert.That((float)userData.GetDouble(0), Is.EqualTo(value));
+        Assert.That((float)userData.GetDouble(), Is.EqualTo(value));
 
         b2World_Step(worldId, 1.0f, 1);