[datafeed] return empty dict when source is fresh avoid crash in the looping task because None returned

     1

\.svn

     2

^build$

     3

^dist$

     4

\.pyc$

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\.pyo$

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\.bak$

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\.old$

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\~$

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\#.*?\#$

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\.swp$

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^doc/book/en/apidoc$