Yes, you could leave it blank because your 1099-B reflects the cost basis as zero, which is not correct. Report the adjusted gain/loss in box g on Schedule D as you noted in your post. Column (g) on Form 8949, Sales and Other Dispositions of Capital Assets, may also contain the adjustment to gain or loss.
If you are using TurboTax online, when you are entering your RSU information, check the box for The cost basis is incorrect or missing on my 1099-B. On the next screen, you will have the option to enter the adjusted cost basis.
If you are using TurboTax CD/download, the process to enter your adjusted cost basis is a little different. After entering your RSU information, you will see a screen, Select any less common adjustments that apply. Select the last one, An adjustment is required for a reason not already covered. Enter your adjustment in the drop-down box. A positive number will increase your gain, a negative number will increase your loss. Because it appears that your RSU sales resulted in a loss, you will want to enter your adjusted cost basis as a negative number.
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