Remove error message on MS Excel 2010

[rds13]

Excel says the file is corrupted if the XML contains empty xml nodes.
Those modifications try to no emit xml nodes if they are empty.

[jurriaan]

I think this is good to merge if it's compliant with the specs.. But I'm not sure..

[trusche]

I can confirm that this gets rid of the error messages in Excel. Would be great if this could be merged!

[randym]

@trusche have you confirmed this against the actual ECMA specs?

[trusche]

@randym No I have not, sorry - I just needed a quick fix. If this isn't spec conform, ignore my comment please.

[jurriaan]

I don't think this is always true for empty elements. When using text runs, Excel itself emits empty elements for the markup.
Are you sure these changes are all needed?
And is it possible to merge/squash your commits?

[spkprav]

@rds13 Hi, I see this is very old, but the issue with line chart still exists, any idea how to solve that?
I tried using this code, but still getting issues at MS Excel 2013, bar chart works fine though.
Any help will be appreciated.