follow up previous commit

lib/bitcoin.py

@@ -335,8 +335,8 @@ def script_to_p2wsh(script):
 
 
 def address_to_script(addr):
-    if is_segwit_address(addr):
     witver, witprog = segwit_addr.decode(SEGWIT_HRP, addr)
+    if witprog is not None:
         assert (0 <= witver <= 16)
         OP_n = witver + 0x50 if witver > 0 else 0
         script = bytes([OP_n]).hex()
@@ -506,7 +506,7 @@ def address_from_private_key(sec):
 
 def is_segwit_address(addr):
     witver, witprog = segwit_addr.decode(SEGWIT_HRP, addr)
-    return witver == 0
+    return witprog is not None and witver == 0
 
 def is_b58_address(addr):
     try: