olevba.py - vba of normal office file decompressed stop by raise exception

[fooofei]

test sample hash : 339cb2460f5b7dcf7122e01f95e8d112

use:
vbaparser = olevba.VBA_Parser(this_file_path)
for v in vbaparser.extract_all_macros():
pass

parse result error message:
File "C:\Python27\lib\site-packages\oletools\olevba.py", line 1051, in decompress_stream
raise ValueError('invalid signature byte {0:02X}'.format(sig_byte))
ValueError: invalid signature byte 00

my opinion :
this file in _VBA_PROJECT_CUR/VBA/StartUp is not contain vba macro , but , we suppose it contains macro , and then to decompressed it . in [ oletools\olevba.py, line 1051 ] , we force to check signature , if not passed , we raise exception . I think we should pre check signature in [ oletools\olevba.py , line 1598 ] , change code [ if len(code_data) > 0 :] to [if len(code_data) > 0 and ord(code_data[0])== 0x01:] , by this, if the stream not contains macro , it will continue decompress the rest stream .