#170 cssclean: may read past the end of css files when corrupted

[Thomas Preud'homme]

Currently, cssclean assumes css files are well formed. For each header
encountered, it thus iterates over all the records the header claims to
be present. However, if the header is corrupted, cssclean will read past
the end of the css file being cleaned. This patch adds a safeguard
against such a situation.

[Thomas Preud'homme]

Here is an improved version of this patch.

Best regards,

Thomas