score: fix dereference of NULL pointer in local_flush_tlb_page()

Don't dereference vma if it's NULL.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Cc: Chen Liqin <liqin.chen@sunplusct.com>
Cc: Lennox Wu <lennox.wu@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>