vlib: fix coverity 274750, part 2

Add another missing null check.

Type: fix
Change-Id: Iec4de548810efe369a6e61b8787131230506cff6
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>

src/vlibmemory/vlib_api_cli.c

@@ -646,7 +646,7 @@ vl_msg_api_process_file (vlib_main_t * vm, u8 * filename,
 	    }
 	  else
 	    {
-	      if (m->replay_allowed)
+	      if (m && m->replay_allowed)
 		vlib_cli_output (vm, "Skipping msg id %d: no handler\n",
 				 msg_id);
 	      break;