gsm: make osmo_imsi_str_valid() NULL-safe
No callers that would pass NULL exist, but let's check against NULL from the
start.
Fixup for recent change I1e94f5b0717b947d2a7a7d36bacdf04a75cb3522.
Change-Id: I111fbf29228929f2cd6ffa06bcb1f69da223224e
diff --git a/src/gsm/gsm23003.c b/src/gsm/gsm23003.c
index 004e20f..3c09aca 100644
--- a/src/gsm/gsm23003.c
+++ b/src/gsm/gsm23003.c
@@ -33,6 +33,8 @@
/* Use unsigned char * to avoid a compiler warning of
* "error: array subscript has type 'char' [-Werror=char-subscripts]" */
const unsigned char *pos = (const unsigned char *)str;
+ if (!pos)
+ return min_digits < 1;
for (len = 0; *pos && len < max_digits; len++, pos++)
if (!isdigit(*pos))
return false;