kconfig: fix mconf segmentation fault

[Sam Ravnborg <sam@ravnborg.org>]

I have found small bug in mconf, when you run it without any argument it
will sigsegv.

Without patch:
$ scripts/kconfig/mconf
Segmentation fault

With patch:
$ scripts/kconfig/mconf
can't find file (null)

Signed-off-by: Marcin Garski <mgarski@post.pl>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
---
 scripts/kconfig/lex.zconf.c_shipped |    2 +-
 scripts/kconfig/zconf.l             |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/kconfig/lex.zconf.c_shipped b/scripts/kconfig/lex.zconf.c_shipped
index 800f8c7..0fdc904 100644
--- a/scripts/kconfig/lex.zconf.c_shipped
+++ b/scripts/kconfig/lex.zconf.c_shipped
@@ -2264,7 +2264,7 @@ FILE *zconf_fopen(const char *name)
 	FILE *f;
 
 	f = fopen(name, "r");
-	if (!f && name[0] != '/') {
+	if (!f && name != NULL && name[0] != '/') {
 		env = getenv(SRCTREE);
 		if (env) {
 			sprintf(fullname, "%s/%s", env, name);
diff --git a/scripts/kconfig/zconf.l b/scripts/kconfig/zconf.l
index cfa4607..187d38c 100644
--- a/scripts/kconfig/zconf.l
+++ b/scripts/kconfig/zconf.l
@@ -265,7 +265,7 @@ FILE *zconf_fopen(const char *name)
 	FILE *f;
 
 	f = fopen(name, "r");
-	if (!f && name[0] != '/') {
+	if (!f && name != NULL && name[0] != '/') {
 		env = getenv(SRCTREE);
 		if (env) {
 			sprintf(fullname, "%s/%s", env, name);
-- 
1.5.1.rc3.20.gaa453