maint: Change the text of the NULLSTR() macro to "<null>"

Eric Blake suggested to change this message to be different from the
glibc's NULL deref protection message in printf to be able to
differentiate errors.

diff --git a/src/internal.h b/src/internal.h
index 4ba0e4194e89e3ee3565e82f01c755cced3b213b..cef3da03282ac3a9c42d5ba06283d40ffeb7704a 100644 (file)
--- a/src/internal.h
+++ b/src/internal.h
@@ -244,7 +244,7 @@
 /*
  * Use this when passing possibly-NULL strings to printf-a-likes.
  */
-# define NULLSTR(s) ((s) ? (s) : "(null)")
+# define NULLSTR(s) ((s) ? (s) : "<null>")
 
 /**
  * TODO: