kconfig: fix mconf segmentation fault

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>

1 files changed, 1 insertions, 1 deletions

diff --git a/scripts/kconfig/zconf.l b/scripts/kconfig/zconf.l
index cfa46077c6b4..187d38ccadd5 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);