checkpatch: handle missing #if open in context

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: Andy Whitcroft <apw@canonical.com>
Tested-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -411,13 +411,15 @@ sub ctx_statement_block {
 
 	my $type = '';
 	my $level = 0;
-	my @stack = ([$type, $level]);
+	my @stack = ();
 	my $p;
 	my $c;
 	my $len = 0;
 
 	my $remainder;
 	while (1) {
+		@stack = (['', 0]) if ($#stack == -1);
+
 		#warn "CSB: blk<$blk> remain<$remain>\n";
 		# If we are about to drop off the end, pull in more
 		# context.