Added check for if range exists when getting progress for resumable u…

[beeradmoore]

As per the resumable upload docs

If nothing has been uploaded yet, the API response will not include the Range header.

If no data has been uploaded you will get an invalid offset 1 when trying to access $range[1]. This fix allows progress to be set only if the range exists in the response header.

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[beeradmoore]

I signed it!

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[beeradmoore]

I signed it!

[beeradmoore]

I signed it! (third times a charm right?)

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