mpool/hugepage CID 1516781: fix strtok usage

I think that in practice, strtok will never return NULL the first time
it is invoked on the options string, but we might as well be defensive
and protect that case.

Signed-off-by: Jeff Squyres <jsquyres@cisco.com>

Author: jsquyres

opal/mca/mpool/hugepage/mpool_hugepage_component.c

@@ -11,7 +11,7 @@
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
  * Copyright (c) 2006      Voltaire. All rights reserved.
- * Copyright (c) 2007-2009 Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2007-2022 Cisco Systems, Inc.  All rights reserved.
  * Copyright (c) 2012-2016 Los Alamos National Security, LLC. All rights
  *                         reserved.
  * Copyright (c) 2016      Intel, Inc. All rights reserved.
@@ -238,9 +238,8 @@ static void mca_mpool_hugepage_find_hugepages(void)
         }
 
         tok = strtok_r(opts, ",", &ctx);
-
         do {
-            if (0 == strncmp(tok, "pagesize", 8)) {
+            if (NULL != tok && 0 == strncmp(tok, "pagesize", 8)) {
                 break;
             }
             tok = strtok_r(NULL, ",", &ctx);