Timestamp issue when video is not opened with the doc

Dear Martin,

Here is a commit to fix the following error: when the doc does not contain the path to the video, or when this
path is not valid, and when the video is opened later, the timeIn is read from the videoEngine where it was never set. The timecode dialog would then display "00:00:00:00" and submitting that breaks the strip sync...

The commit fixes that by reordering the calls in openVideoFile.

Best regards,

Timothée