If the #if opening statement is not in the context then the context stack
can be empty.  Handle this by ensuring there is always a blank entry in
the stack.
Signed-off-by: NAndy Whitcroft <apw@canonical.com>
Tested-by: NDhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>