Fix creation of the report's file name from the mangling of the user name

Fix creation of the report's file name from the mangling of the user name

The directory and file name to store a user's report is produced by
replacing any character but the letters, digits and a few safe
characters from the user name. But that name mangling was not dealing
properly with consecutive invalid characters. The result was, at best,
a truncated file name (without any real consequence) or, at worst, an
invalid character left in the file name.