utils: assert on streq for NULL pointers

We have streq_null for that purpose

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

src/utils.h

@@ -66,6 +66,7 @@ istrncmp(const char *a, const char *b, size_t n);
 static inline bool
 streq(const char *s1, const char *s2)
 {
+    assert(s1 && s2);
     return strcmp(s1, s2) == 0;
 }