there was no democrat running for corporation commissioner so i'd assume it would be the same as leaving that blank.

If you did not vote this, you would have had to make a selection or it would not have been voted.

When taking the ballot to the e-scan machine, if any race on a single ballot sheet is not voted, the machine kicks it back out and states what's up on the screen: an unvoted race, an over-voted race (two or more selections filled in instead of one), etc, so you can double-check the ballot.

You can fix the ballot at that time or cast the ballot as-is (just a button on the machine to confirm to feed it back in and poll worker can assist) - if it's blank that section won't be counted unless you vote it, if it's over-voted also that section/race won't be counted it will be invalid..to fix that the poll worker spoils the ballot and issues you a new one.

Straight ticket is only going to mark your partisan races not the questions or judges and stuff also.

And there is no straight-ticket option in primaries of course because those are entire partisan ballots.