another sqlmap crash

[stormwin]

[16:58:00] [CRITICAL] unhandled exception in sqlmap/1.0-dev-f3aa09c, retry your run with the ****** development version from the GitHub repository. If the exception persists, please send by e-mail to 'sqlmap-users@lists.sourceforge.net' or open a new issue at 'https://github.com/sqlmapproject/sqlmap/issues/new' with the following text and any information required to reproduce the bug. The developers will try to reproduce the bug, fix it accordingly and get back to you.
sqlmap version: 1.0-dev-f3aa09c
Python version: 2.6.5
Operating system: posix
Command line: sqlmap.py -u ********************************** --level 7 --risk 5 --dbms=mysql --sql-shell --flush-session --fresh-queries --hex
Technique: BOOLEAN
Back-end DBMS: MySQL (fingerprinted)
Traceback (most recent call last):
File "/root/sqlmap/_sqlmap.py", line 72, in main
start()
File "/root/sqlmap/lib/controller/controller.py", line 568, in start
action()
File "/root/sqlmap/lib/controller/action.py", line 139, in action
conf.dbmsHandler.sqlShell()
File "/root/sqlmap/plugins/generic/custom.py", line 102, in sqlShell
output = self.sqlQuery(query)
File "/root/sqlmap/plugins/generic/custom.py", line 48, in sqlQuery
output = inject.getValue(query, fromUser=True)
File "/root/sqlmap/lib/request/inject.py", line 428, in getValue
value = __goInferenceProxy(query, fromUser, batch, unpack, charsetType, firstChar, lastChar, dump)
File "/root/sqlmap/lib/request/inject.py", line 322, in __goInferenceProxy
outputs = __goInferenceFields(expression, expressionFields, expressionFieldsList, payload, charsetType=charsetType, firstChar=firstChar, lastChar=lastChar, dump=dump)
File "/root/sqlmap/lib/request/inject.py", line 121, in __goInferenceFields
output = __goInference(payload, expressionReplaced, charsetType, firstChar, lastChar, dump, field)
File "/root/sqlmap/lib/request/inject.py", line 93, in __goInference
count, value = bisection(payload, expression, length, charsetType, firstChar, lastChar, dump)
File "/root/sqlmap/lib/techniques/blind/inference.py", line 538, in bisection
infoMsg = "\r[%s] [INFO] retrieved: %s %s\n" % (time.strftime("%X"), filterControlChars(finalValue), " " * len(finalValue))
TypeError: object of type 'NoneType' has no len()