Fixes #4: internal_code is optional in 04 lines

Author: Alexis de Lattre

cfonb/parser/common.py

@@ -151,7 +151,7 @@ class ParserContent04(Parser):
     _regex = [
         ('record_code',     '(04)',  2),
         ('bank_code',       G_N,     5),
-        ('internal_code',   G_AN,    4),
+        ('internal_code',   G_AN_,   4),
         ('desk_code',       G_N,     5),
         ('currency_code',   G_A_,    3),
         ('nb_of_dec',       G_N_,    1),