Fix bug on previous release

Fix fully iterating over elements

Some elements, such as pixel data, might have a nil value. Furthermore the FindElementByTagNested does not adhere to the internal documentation to fully exhaust the  iterators goroutine.

v1.0.8 Added optional handling of the number of frames for GetPixelDataReader

Merge pull request #1 from pedrogameiro/optional_num_frames

Add optional handling of number of frames and total bytes for the pix…

v1.0.7: Added pixel data size getter

Restore original pixel data parsing and remove unnecessary changes

v1.0.6: Added pixel data size getter

Restore original pixel data parsing and remove unnecessary changes

Testing pixel data reader

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v1.0.4.test2

Fix buffer

v1.0.4.test

Try to simply pass the byte data of the frames