[IA64] virt_to_page() can be called with NULL arg

It does not return NULL when arg is NULL.

Signed-off-by: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-off-by: Kirill Korotaev <dev@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

include/asm-ia64/pgalloc.h

@@ -137,7 +137,8 @@ pmd_populate_kernel(struct mm_struct *mm, pmd_t * pmd_entry, pte_t * pte)
 static inline struct page *pte_alloc_one(struct mm_struct *mm,
 					 unsigned long addr)
 {
-	return virt_to_page(pgtable_quicklist_alloc());
+	void *pg = pgtable_quicklist_alloc();
+	return pg ? virt_to_page(pg) : NULL;
 }
 
 static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm,