10096 kstat update routines shouldn't check for NULL kstat

@@ -21,10 +21,14 @@
 
 /*
  * Copyright (c) 2004, 2010, Oracle and/or its affiliates. All rights reserved.
  */
 
+/*
+ * Copyright (c) 2018, Joyent, Inc.
+ */
+
 #include <sys/types.h>
 #include <sys/stream.h>
 #include <sys/cmn_err.h>
 #define _SUN_TPI_VERSION 2
 #include <sys/tihdr.h>

@@ -58,11 +62,11 @@
         netstackid_t    stackid = (netstackid_t)(uintptr_t)kp->ks_private;
         netstack_t      *ns;
         sctp_stack_t    *sctps;
         mib2_sctp_t     sctp_mib;
 
-        if (kp == NULL|| kp->ks_data == NULL)
+        if (kp->ks_data == NULL)
                 return (EIO);
 
         if (rw == KSTAT_WRITE)
                 return (EACCES);