Fix german typos

So this is just a fix for de-AT / de-DE/   index.html and empty.html
The typos don't influence the functionality, but they are "ugly" ... I got the mail, that pointed to them yesterday at 22:50. Which is 21:50 your time :) ... first commit.

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I found some more :) second commit.

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How fast can we update tiddlywiki.com ... will we need something like a "sub version number" for these fixes?