fix: issue2551387 - TypeError: not indexable. Fix crash due to uninitialized list element on a (Mini)FieldStorage when unexpected input is posted via wsgi. This doesn't happen when running roundup-server. It might happen under other front ends. Moved the code that sets '.list = [] if .list == None' to the main flow. Added an exception hander that logs the value of self.form if self.form.list raises an AttributeError. This exception should never happen if I understand the code correctly (but I probably don't). Fixed a number of test cases that were broken because I was calling Client and passing '[]' rather than a cgi.formStorage object. Added test cases: create a FileStorage (self.form) with .list = None. check AttributeError exception and verify logging. Problem reported and debugged by Christof Meerwald.