Fix T42411: Camera inside volume + particle dupli (object/group) doesn't work

The issue was caused by missing current object instance initialization after
object was ignored for instance push.

intern/cycles/kernel/geom/geom_bvh_volume.h

@@ -277,6 +277,7 @@ ccl_device bool BVH_FUNCTION_NAME(KernelGlobals *kg,
 					}
 					else {
 						/* pop */
+						object = OBJECT_NONE;
 						nodeAddr = traversalStack[stackPtr];
 						--stackPtr;
 					}