staging: dgrp: check for NULL pointer in (un)register_proc_table

register_proc_table and unregister_proc_table didn't deal with the
possibility that the *table pointer could be NULL.  Check for this and
return if table is NULL.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Bill Pemberton <wfp5p@virginia.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/dgrp/dgrp_specproc.c

@@ -229,6 +229,9 @@ static void register_proc_table(struct dgrp_proc_entry *table,
 	int len;
 	mode_t mode;
 
+	if (table == NULL)
+		return;
+
 	for (; table->id; table++) {
 		/* Can't do anything without a proc name. */
 		if (!table->name)
@@ -297,6 +300,9 @@ static void unregister_proc_table(struct dgrp_proc_entry *table,
 	struct proc_dir_entry *de;
 	struct nd_struct *tmp;
 
+	if (table == NULL)
+		return;
+
 	list_for_each_entry(tmp, &nd_struct_list, list) {
 		if ((table == dgrp_net_table) && (tmp->nd_net_de)) {
 			unregister_dgrp_device(tmp->nd_net_de);