Fix errors in mouse detection when removing collision object from tree

Now behaves the same way as ui elements, mouse exit is skipped when the
object is removed from the tree.

scene/main/viewport.cpp

@@ -2687,6 +2687,10 @@ void Viewport::_drop_physics_mouseover(bool p_paused_only) {
 		if (o) {
 			CollisionObject2D *co = Object::cast_to<CollisionObject2D>(o);
 			if (co) {
+				if (!co->is_inside_tree()) {
+					to_erase.push_back(E);
+					continue;
+				}
 				if (p_paused_only && co->can_process()) {
 					continue;
 				}
@@ -2705,7 +2709,9 @@ void Viewport::_drop_physics_mouseover(bool p_paused_only) {
 	if (physics_object_over) {
 		CollisionObject *co = Object::cast_to<CollisionObject>(ObjectDB::get_instance(physics_object_over));
 		if (co) {
-			if (!(p_paused_only && co->can_process())) {
+			if (!co->is_inside_tree()) {
+				physics_object_over = physics_object_capture = 0;
+			} else if (!(p_paused_only && co->can_process())) {
 				co->_mouse_exit();
 				physics_object_over = physics_object_capture = 0;
 			}