Switch over to use use blocks from nostrdb

This is still kind of broken until queries are switched over to nostrdb.
Will do this next

Signed-off-by: William Casarin <jb55@jb55.com>

nostrdb/src/bolt11/bolt11.c

@@ -133,7 +133,8 @@ static struct bolt11 *decode_fail(struct bolt11 *b11, char **fail,
     va_list ap;
 
     va_start(ap, fmt);
-    *fail = tal_vfmt(tal_parent(b11), fmt, ap);
+    if (fail)
+        *fail = tal_vfmt(tal_parent(b11), fmt, ap);
     va_end(ap);
     return tal_free(b11);
 }