Get rid of the pointless null checks on collision listeners. Add warning about synchronicity for PhysicsActor.OnCollisionUpdate event doc

OpenSim/Region/Framework/Scenes/SceneObjectPart.cs

@@ -2083,10 +2083,6 @@ namespace OpenSim.Region.Framework.Scenes
         public void PhysicsCollision(EventArgs e)
         {
             // single threaded here
-            if (e == null)
-            {
-                return;
-            }
 
             CollisionEventUpdate a = (CollisionEventUpdate)e;
             Dictionary<uint, ContactPoint> collissionswith = a.m_objCollisionList;

OpenSim/Region/Framework/Scenes/ScenePresence.cs

@@ -3296,9 +3296,6 @@ namespace OpenSim.Region.Framework.Scenes
         // Event called by the physics plugin to tell the avatar about a collision.
         private void PhysicsCollisionUpdate(EventArgs e)
         {
-            if (e == null)
-                return;
-
             //if ((Math.Abs(Velocity.X) > 0.1e-9f) || (Math.Abs(Velocity.Y) > 0.1e-9f))
             // The Physics Scene will send updates every 500 ms grep: PhysicsActor.SubscribeEvents(
             // as of this comment the interval is set in AddToPhysicalScene

OpenSim/Region/Physics/Manager/PhysicsActor.cs

@@ -140,7 +140,13 @@ namespace OpenSim.Region.Physics.Manager
         public event VelocityUpdate OnVelocityUpdate;
         public event OrientationUpdate OnOrientationUpdate;
         public event RequestTerseUpdate OnRequestTerseUpdate;
+
+        /// <summary>
+        /// Subscribers to this event must synchronously handle the dictionary of collisions received, since the event
+        /// object is reused in subsequent physics frames.
+        /// </summary>
         public event CollisionUpdate OnCollisionUpdate;
+
         public event OutOfBounds OnOutOfBounds;
 #pragma warning restore 67