Sigil claims: epub invalid if <!DOCTYPYE... section is not present and &nbsp; entities appear in file

[GoogleCodeExporter]

Please read http://code.google.com/p/sigil/wiki/ReportingIssues for
information about submitting a good bug report.

What steps will reproduce the problem?
1. Create empty file in Sigil
2. Type   entities in the html editior;
3. Delete <!DOCTYPE section from the html file (from the top)
4. Save file and validate the epub with some epub validator (e.g. 
http://www.epubvalidator.com) 
5. Update content.opf to make epub valid (add dc:title and dc:language in 
<metadata> ... validator complains about that
6. After few checks you will see that epub validator accepts the file but with 
every file opening by Sigil it claims that file is invalid.

What is the expected output? What do you see instead?
Expected output - not complaining about the problem

What version of the product are you using? On what operating system?
Windows 7, Sigil 0.7.3

P.S. This but also presents other Sigil bug which is: Empty file created by 
sigil is not valid according to EPUB standard (http://www.epubvalidator.com) 
Seems like FlightCrew is not so strict like EpubCheck software which detects 
more epub incnsitencies

P.S.2 Please exceed my attachment quota! I've tried to attach file that could 
present the issue but I'v got message 'Issue attachment storage quota exceeded.'

Original issue reported on code.google.com by grzech...@gmail.com on 8 Sep 2013 at 11:34

[GoogleCodeExporter]

Using a named HTML entity requires a DOCTYPE to be defined for EPUB 2.1.  Use & 
# 160; to avoid needing the DOCTYPE.

Original comment by daveheil...@gmail.com on 11 Sep 2013 at 4:25

• Changed state: Done