parse buffer as header if passed as arg to next()

diff --git a/deltatar/crypto.py b/deltatar/crypto.py
index e6374ad..0226a48 100755 (executable)
--- a/deltatar/crypto.py
+++ b/deltatar/crypto.py
@@ -531,6 +531,8 @@ class Decrypt (Crypto):
 
 
     def next (self, hdr):
+        if isinstance (hdr, bytes) is True:
+            hdr = hdr_read (hdr)
         paramversion = hdr ["paramversion"]
         if self.key is None:
             super().next (self.password, paramversion, hdr ["nacl"])